The evolution of the calendar how to use a calendar today

The evolution of the calendar how to use a calendar todayPerfecting a method of foretelling and predicting the passage of time preoccupied our ancestors from the earliest recorded history. The unending journey of the Sun, Moon and stars across the great expanse of the sky provides clues for numerous methods of marking time, the most obvious to primitive man being the passage of a day (light/dark) and that of a month (based on phases of the Moon).

Measuring the exact length of a year is difficult, but for our ancient ancestors’ less stringent parameters, such as when a certain tree would bloom, was sufficient proof to denote the beginning of a new year.

The ancient Egyptians knew that to calculate an accurate measurement of a year, it was necessary to take note of where the stars are in the sky at any given time. Specifically, the priests of Egypt used Sirius, the Dog Star, to predict the flooding of the Nile annually, which gave them the appearance of being able to foretell this event. Studying Sirius also enabled the Egyptians to become the first civilization to switch from a lunar to a solar calendar.

The ancient Babylonians utilized a lunar calendar. Even today, the Muslim and Jewish calendars remain lunar-based. Nice, if you like tradition, but using a lunar calendar poses a major problem as well. A lunar month is 29.5 days, meaning 12 lunar months add up to 354 lunar days, which is about 11 days short of a solar year. To solve this problem, some lunar calendars add an extra month every now and then to make up for lost time, which is how it is handled with the Jewish calendar.

However, the Egyptian priests’ study of Sirius allowed them to count the exact number of days in a solar year. They then arranged the lunar months into 12 month intervals, making each of them 30 days in length with five added days at the end of the year.

Sounds pretty good, but there is a problem, which is that every four years Sirius shows up a day late. The reason for this is that the solar year is really closer to 365 days and six hours, which the Egyptians never took into account, though they were aware of the issue. This resulted in the calendar taking a backward slide as a lunar one would do, only at a much slower pace.

By the time of the Roman Empire under Julius Caesar, the calendar, which was out of sync by about three months, was in desperate need of tweaking. With the help of Sosigenes, a renowned astronomer from Alexandria, Julius Caesar started a new calendar on January 1, 45 B.C.- a calendar that came closer to the solar year than any of its predecessors and became known as the “Julian Calendar”.

Sosigenes informed Caesar that the actual length of the solar year is 365 days and six hours, as the Egyptian priests had known. Sosigenes felt the logical solution was to simply add a day to February, the shortest of the Roman months, every fourth year. This made up the difference, and with this clever idea the leap year was born.

This calendar quickly spread across the entire Roman Empire, and was also used throughout Christendom for centuries. And yet, once again, an error popped up. It turns out, that the solar year isn’t actually 365 days and six hours after all. It’s actually 365 days, 5 hours, 48 minutes and 46 seconds. This only amounts to a discrepancy of a single day over 130 years, but when you’re talking millennia you have no choice but to nitpick.

By the 1500s, the seemingly minor glitch of calculating the solar year to be 11 minutes and 14 seconds shorter than it is led to about a 10 day gap between the calendar and the real solar year. This posed a particular problem around the equinoxes, which were occurring 10 days earlier than the dates on the calendar denoted they should be.

Clearly something needed to be done, so Pope Gregory XIII asked Christopher Clavius, a Jesuit astronomer, to help him solve the problem. Quickly discovering that the error in question amounts to 3 days over a span of 400 years, he devised a brilliant solution to the predicament.

The ingenious astronomer put forth the suggestion that years ending in ’00 should from that point on only be leap years if they could be divided by 400. By doing so, three leap years are eradicated every three centuries, providing a tidy solution to the problem.

The proposal, named after the Pope responsible for hiring its mastermind (rather than the mastermind), was put into use in the Papal States in 1582. The Gregorian calendar was quickly picked up by Spain, Portugal, France and the Italian states the following year.

This was a time of great religious upheaval in Europe, and many of the Protestant states were in no great rush to concede that the Bishop of Rome was right about anything. The Lutheran states of Germany finally got around to making the change in 1700, while Great Britain put it off until 1752. Even though by that point Britain had accrued a sizable gap of 11 days, many people protested violently when the change was made.

Russia did not convert to the Gregorian calendar until after the Russian Revolution in 1917. (The funny thing was, in 1908, the Russian Olympic team arrived 12 days late to the London Olympics because of it.)

Further technological advances in the 20th century made it possible to hone the accuracy of the Gregorian calendar even more. For instance, it has been suggested that to fix a small error in the Gregorian calendar, one day should be added every 3,323 years, and years divisible by the number 4000 will not be leap years.

So, the next time you’re scribbling down your next dental appointment on your handy-dandy calendar, take a moment to appreciate its long and noble evolution. The calendar so casually given to you during the Holidays sits in your hands thanks to the input of Egyptian priests, Julius Caesar and co. and a Pope and his trusty Jesuit astronomer.

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  • On the other side of the pond a calendar had been devised, not unlike the one the Romans had come up with, by a culture in Central America called the Olmecs, and was fined tuned around the first century AD by the Mayans. The Mayans, having concluded that there were 365 days in a year, fashioned a calendar consisting of 18 months including 20 days each. They rounded out the year by adding five days at the end which were considered to be very unlucky. Another aspect unique to the Mayan calendar is what is called the “Calendar Round”, which is a cycle lasting 52 years in which every day has its own individual name – none are repeated.

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Why Do We Use a Calendar?

Have you ever thought how life would be without a calendar? Just imagine what would happen if all the world’s calendars suddenly disappeared…we would be clueless and helpless at the same time because we are so used to it. We, humans have been using this tool since the beginning of the civilization, however the calendars have underwent a sea of change and various revolutionary theories from renowned historians and astronomers have contributed into evolving the calendar into what it is today.

Julius Caesar introduced a calendar in 45 B.C.E and the most interesting fact about this calendar was that it also started with 1 January. Before the introduction of the Gregorian calendar, which was named after Pope Gregory XIII in 1582, the Julian calendar was widely used. As the Julian calendar had some imperfections, it was finally reformed and named as the Gregorian calendar which is used around the world today.

Although various historians and astronomers have many times challenged the theory on which the Gregorian calendar is based and different types of calendars have been proposed, until now the Gregorian calendar has been widely accepted and considered relevant around the world.

So, the question is – why do we use a calendar?

When it comes to determining the significance and use of calendar in people’s lives, you will discover that different people use it for different purposes. Although the basic need of a calendar is to keep a track of the present day, month, and year; basically identify the particular time in which we are living or existing, there are several other reasons for which people use a calendar:

  • Planning the daily activities
  • Keeping a track of events
  • Staying organized and enhancing productivity
  • Planning efficiently and meeting the deadlines
  • Remembering birthdays and keeping commitments
  • Managing the daily schedule
  • Remembering important dates
  • Alleviating the anxiety and stress
  • Knowing the important festival dates

How did technology influence the use of calendar?

In the past, we only had the wall calendars that helped us remember the dates and add important notes besides the dates to keep a track of things. However with the advent of technology, the calendar also got a makeover and it slowly shifted its position from the wall and found its place inside the modern portable gadgets like laptops, computers, and smartphones.

Although we still have the humble wall calendars in our homes and offices, the personal calendars in our mobile devices has enabled us to organize our tasks and schedule the important activities for particular days, months or keep an efficient track of the annual events. The enhanced calendar tools further help us customize the calendar, break down each day into hours and distribute our time for important events and meetings.

The modern man cannot imagine life without a calendar, the one that silently hangs on the wall as well as the one he carries with him in his phone and it plays several roles such as that of an interactive day planner, event organizer, special dates reminder, productivity booster, and a buddy that makes sure that you live each moment to the fullest!

How can we be absolutely sure our seventh day is still the Sabbath? Could the calendar have been changed? Is the seventh day of the week the same as in the time of Christ and Moses? This is very important. The seven day week, as well as the Bible Sabbath, had a common origin in history. Both originated at the Creation of our world. Scientists, historians, and astronomers affirm that the seven day weekly cycle has continued uninterrupted on down to our own day.

Both ancient and modern languages support the regular, weekly cycle. And, in at least 108 of them, the name for the seventh day of the week is not Saturday, or Saturn Day, but Sabbath! Let me give just a few examples:

Ancient Syriac: shabatho, Babylonian: sabatu, Arabic: assabt, Etheopic: sanbat, Armenian: shapat, Polynesian: hari sabtu, Swahili: assabt, Latin: Sabbatum, Italian: Sabbato, Spanish: Sabado, Russian: Subbota, Polish: Sobota, Assyrian: Sabata, Tigre: Sanbat, Kurdish: Shamba, Georgian: Shabati, Morduin: Subbota, Portuguese: Sabbado, New Slovenian: Sobota, Prussian: Sabatico.

So you see, the languages of the world also remind us of God’s holy Sabbath day. Most languages of the world still call Saturday the Sabbath. All of these names mean “Sabbath” or “rest day” in their various languages. Except for those languages that have adopted the pagan names for the days of the week, the seventh day is still called the Sabbath, as the Lord named it at the time of the creation of the world.

Why the Seven-day weekly cycle?

Actually, the only reason we have a seven-day weekly cycle in the first place is that God created it during the creation week in the beginning. Have you ever wondered why we have the week? We have the yearly cycle because of the seasons, and the monthly cycle because of the moon. But nothing in nature indicates a seven-day weekly cycle. If the theory of evolution were correct, every nationality would, by the law of averages, have come up with a different weekly cycle, some 5 days, some 10 days, etc. But we all have the same seven-day weekly cycle because God established it at the Creation and it has continued to the present day.

Has the calendar been changed? Yes, but the weekly cycle has never been changed. The Julian calendar was in use when Jesus was on earth. The calendar, which continued in use for 15 centuries was not accurate in length of its year, for it was a quarter hour too long. By 1582, it was 10 days off. Pope Gregory initiated a change in the calendar by going to the Gregorian Calendar, and to make up for the error in the Julian calendar, 10 days were added to the calendar. In October, 1582, Thursday the 4th was followed by Friday the 15th in Italy and a few other countries. England and America changed its calendar in 1752 and Russia finally in 1914. Yet the weekly cycle was never affected. During the time that England, Russia, and Italy had different calendars, Sunday, Monday, and Tuesday were always the same in each country. [As a side note, the beginning of the year began March 1st under the Julian calendar, whereas he beginning of the year begins January 1st under the Gregorian calendar].

We do the same thing today, because every four years we change our calendar; it’s called “leap year.” At the end of February, we add one day every four years to our calendar. But notice the days of the week never change, it is only the number of the day that changes. For example, when that extra day is added, it might go from Thursday the 28th to Friday the 29th; the days of the week remain the same, only the numbers of the day change. There is no difference when 10 days are added to the calendar as well.

History has exact calendar records going back to Julius Caesar, several decades before Christ, and the weekly cycle has always remained intact. We have exactly the same weekly cycle today as was used in Jesus’ day, and Jesus said that the day then called the Sabbath by the Jews, the seventh day of the week, was His day, the true Lord’s Day. Yes, the amount of days in a month has changed, the amount of days in a year has changed, the amount of weeks in a month has changed, the amount of weeks in a year has changed, the amount of months in a year has changed. But the amount of days in a week has never changed since man was first created on earth.

Scientific and Historical Evidence

Our heavenly Father has given us more than scientific and historical evidence, though. He has given us the Jews! Every other Near East ethnic group has disappeared – the Hitites, Canaanites, Amorites, Amalekites, Perizzites, Jebusites, Sumarians, Babylonians, Assyrians, Moabites, Philistines – but the Jews remain and, with them, the seventh day Sabbath. They have faithfully kept it since the time of Moses, 3500 years ago, and have continued to keep track of the Sabbath each week. Any Jew will tell you that the seventh day is the Sabbath, and that it falls on the Saturday of each week. It would be absolutely impossible to mix up a whole nationality overnight and have them all wake up unified and worshipping on another day, thinking it was the Sabbath. Moreover, since Jesus has commanded us to worship on that day to show allegiance to Him, don’t you think He would preserve its identity?

Christ risked his life and mission to rescue the Sabbath from the legalistic perversions of the Pharisees, and to show what was in harmony with the original law (Matthew 12:1-13, Mark 1:21-34; 2:23-28; 3:1-5; 6:1-6, Luke 4:16-18,31-41; 6:1-10; 13:10-17; 14:1-6, John 5:5-18; 9:13-16). He spoke no word implying the abolition of the Sabbath day. Why should he so carefully define, defend, and clear from superstitious accretions the Sabbath if it was to be abrogated? No one repairs a house as a preliminary to burning it down, or re-etches the letters of a monument prior to its destruction. Now, if the Sabbath day was to cease following Jesus’ death, this exhortation would be totally uncalled for. But such is not the case, because the Sabbath day will continue to be a day of rest, worship, and rejuvenation for God’s people (Isaiah 66:22-23). The Sabbath was intended by God to be a day of freedom, a day of delight, and the highlight of the week (Isaiah 58:13-14).

The Gregorian calendar, the calendar system we use today, was first introduced in 1582. To make up for the inaccuracies of its predecessor, the Julian calendar, a number of days had to be skipped.

The evolution of the calendar how to use a calendar today

September 1752 in North America

Too Many Leap Years

The Gregorian calendar, also known as the Western or Christian calendar, is the most widely used calendar in the world today.

Its predecessor, the Julian calendar, was replaced because it did not correctly reflect the actual time it takes the Earth to circle once around the Sun, known as a tropical year. In the Julian calendar, a leap day was added every four years, which is too frequent.

Although it is not perfect either, today’s Gregorian calendar uses a much more accurate rule for calculating leap years.

Skipped Several Days

Over the centuries since its introduction in 45 BCE, the Julian calendar had gradually drifted away from astronomical events like the vernal equinox and the winter solstice. To make up for this error and get the calendar back in sync with the astronomical seasons, a number of days had to be dropped when the Gregorian calendar was adopted.

In North America, for example, the month of September 1752 had only 19 days, as the day count went straight from September 2 to September 14 (see illustration).

Number of Lost Days Varied

The papal bull issued by Pope Gregory XIII in 1582 decreed that 10 days be skipped when switching to the Gregorian calendar. However, only five countries adopted the new calendar system that year—namely, Italy, Poland, Portugal, Spain, and most of France.

Since the discrepancy between the Julian calendar year and the astronomical seasons kept growing over time in the centuries that followed, more days had to be skipped in countries that switched to the Gregorian calendar in later years. Some countries, such as Russia, Greece, and Turkey, switched calendars as late as the early 20th century, so they had to omit 13 days (see table).

Switch Took More Than 300 Years

In total, more than three centuries passed until the Gregorian calendar had been adopted in all countries, from 1582 to 1927. The table below shows when the calendar reform occurred in some countries, including the first and the last.

Gregorian Calendar Introduction Worldwide

Note: The list only includes countries that officially used the Julian calendar before the Gregorian calendar was introduced; countries that switched from a different calendar system to the Gregorian calendar, such as Saudi Arabia in 2016, are excluded. In some cases, it shows a simplified version of events. Each country is listed by its current name, although its official name may have changed since the calendar reform.

Calendar Chaos

The delay in switching meant that countries followed different calendar systems for a number of years, resulting in differing leap year rules.

In the Gregorian calendar, most years that are evently divisible by 100 are common years, but they are leap years in the Julian calendar. This meant that the years 1700, 1800, and 1900 were leap years in countries still using the Julian calendar at the time (e.g., Greece), while in countries that had adopted the Gregorian calendar (e.g., Germany), these years were common years.

Double Leap Year

Sweden and Finland even had a “double” leap year in 1712. Two days were added to February, creating February 30, 1712 after the leap day in 1700 had erroneously been dropped, and the calendar was not synchronized with either the Julian or the Gregorian system. By adding an extra leap day in 1712, they were back on the Julian calendar. Both countries introduced the Gregorian calendar in 1753.

Many Variations

In some non-western countries, the calendar reform took on many different guises to accommodate differing cultural and historical contexts. For example, Japan replaced its lunisolar calendar with the Gregorian calendar in January 1873 but decided to use the numbered months it had originally used rather than the European names.

The Republic of China (1912-1949) initially adopted the Gregorian calendar in January 1912, but it wasn’t actually used a due to warlords using different calendars. However, the Nationalist Government (1928-1949) formally decreed the adoption of the Gregorian calendar in China in January 1929.

13 Days Behind Today

Currently, the Julian calendar is 13 days behind the Gregorian calendar. This gap will change in the year 2100 when the discrepancy will increase to 14 days.

Please note: Today, the term Julian calendar is also used to describe a calendar showing day numbers.

Create Calendar With Holidays

Calendar History

  1. Gregorian Calendar
  2. Julian Calendar
  3. Switch from Julian to Gregorian
  4. Roman Calendar
  5. What Do CE and BCE Mean?
  6. When Do Decades Start?
  7. Did the Millennium Start in 2000 or 2001?’s Calendar Generator and PDF Calendars automatically take into account the dates various countries changed to the Gregorian calendar. The Julian Calendar is shown by default for years before the switch.

Leap Years

  1. What Is a Leap Year?
  2. Leap Day is February 29
  3. Customs & Traditions
  4. Common Year vs. Leap Year
  5. Born on February 29
  6. February 30 Was a Real Date

Calendars Worldwide

  1. Gregorian Calendar
  2. Julian Calendar
  3. Hindu Calendar
  4. Buddhist Calendar
  5. Islamic Calendar
  6. Jewish Calendar
  7. Persian Calendar
  8. Chinese Calendar
  9. Coptic Calendar
  10. Ethiopian Calendar
  11. Revised Julian Calendar
  12. Mayan Calendar

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The evolution of the calendar how to use a calendar today

Strawberry Moon in June

The Full Moon in June is named after the wild strawberries that start to ripen in early summer. It is also called Rose Moon, Hot Moon, or Mead Moon,

The evolution of the calendar how to use a calendar today

The Gregorian Calendar

The Gregorian calendar is the internationally accepted civil calendar that was first adopted in 1582.

The evolution of the calendar how to use a calendar today

June Solstice Traditions

In many Northern Hemisphere cultures, the June solstice is associated with holidays, feasts and celebrations.

The evolution of the calendar how to use a calendar today

Full Moon Names

Full Moons had given names in many ancient cultures. The Full Moon names we use today often reflect nature like Harvest Moon.

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The ancient Maya created a system of timekeeping based on astronomy that’s still used today.


Eight years ago, the world was supposed to end. At least that’s what some interpreters of the ancient Maya calendar believed. They noted that the Maya Long Count calendar seemed to be running out of days, and would end on Dec. 21, 2012. Various doomsday scenarios, asteroids featuring prominently among them, were forecast.

Of course, the winter solstice of 2012 came and went with little to show for it. The Maya calendar simply ticked over to a new b’ak’tun, equal to about 394 years, and the world continued.

The obsession with the Maya calendar and doomsday makes sense from one perspective. After all, Maya religious observances did rely heavily on their amazingly accurate calendar. But the year 2012 likely never figured into Maya eschatology, the study of end times — that one was all us.

The Maya developed a detailed system of timekeeping based largely on astronomical measurements that let them time agricultural events, religious observances and more. Their richly detailed calendar has drawn archaeological interest for decades, as both an example of Maya ingenuity and for the insights into their culture it contains.

The calendar was intimately interwoven with their religion and cosmology, lending it an aura of mystical insight that resonates today. Spiritual though it may seem, the real origin of the calendar is firmly grounded in science.

Finding Time in the Stars

The Maya were excellent astronomers — they erected entire buildings to serve as observatories and created detailed tables cataloging the movements of the moon, Mars and other planets. Maya astronomical calculations even accurately dated a 1991 solar eclipse . Observations like these formed the basis for their calendar; the celestial clock provided a reasonably accurate means of measuring the passage of time.

The Maya made use of several interlocking calendars, though they likely didn’t invent them. There are strong similarities between Maya calendars and those used by older Central American civilizations like the Olmec. The Maya appear to have simply expanded upon these.

The Maya used two separate calendars that counted off days, the haab and the tzolk’in (though the latter is a term modern archaeologists bestowed on the calendar; the Maya use several different names for it). The haab consists of 18 months of 20 days each, with another month of five days called the Wayeb, for a total of 365 days. The Wayeb was considered a dangerous time, and the Maya would make offerings and conduct religious observances to ward off ill-fortune. The tzolkin has 260 days, and consists of 20 named days and 13 numbers, with each combination of name and number occurring once.

The Maya still use these two calendars today to guide their agricultural season and to dictate the timing of religious observances. Members of their culture have been keeping count of the days for well over two thousand years — an unbroken string of timekeeping.

As with the Maya of today, the calendar held immense practical value to their forebears. It allowed them to calculate when to begin planting, harvesting and other agricultural activities each year, and informed the elaborate schedule of rituals and ceremonies to various deities that were at the center of their culture.

Much of the Maya’s understanding of time came from the movement of celestial bodies. Like us, the passage of the Sun informed the length of a day and the time between solstices was a year. But the Maya also tracked the movements of other bodies with extreme precision. The few surviving pieces of Maya writing contain tables cataloging the movements of planets and almanacs that attempted to make forecasts for the future based on them.

The Dresden Codex , the oldest surviving book written in the Americas, contains tables charting the movements of Venus, Mars and the Moon . The Maya also calculated the occurrence of lunar eclipses based on observations and tracked the motion of Jupiter and Saturn . The regular motion of the planets likely formed the basis for much of the Maya’s religious calendar, as they aligned important events with the position of the planets in the night sky.

Keeping Time

The haab and tzolk’in calendars are used together to create a cycle called the Calendar Round, which lasts about 52 years, or 18,980 days. That number is the least common multiple of 260 and 365, or the first point at which the two calendars meet. After one Calendar Round is finished, another begins.

Because the intertwined haab and tzolk’in repeat every 52 years, the Maya needed another way to keep track of longer periods of time. This led them to develop a completely separate system of time-keeping, the Long Count.

The Long Count is a base-20, or vigesimal number system, with one exception. As with our own base-10 number system, there’s likely a simple explanation for this. We have five fingers on each hand, and two hands — we chose to count using our fingers, while the Maya used fingers and toes.

The base unit of the Long Count is a day, called a kin. Twenty kin is a uinal (or winal), 18 uinal is a tun, 20 tun is a k’atun and 20 k’atun is a b’ak’tun. The odd 18 count is likely to bring a tun closer to a solar year — one tun is 360 days, rather than the 400 it would be if counting by 20.

The Maya wrote Long Count dates from left to right, beginning with the largest number. For example, Dec. 21 is written as, or 13 b’ak’tun, 0 k’atun, 8 tun, 2 uinal and 2 kin. That count also allows us to trace back to the exact year the Maya believe our current world began on: 3114 B.C., about 600 years before the Pyramids of Giza were built.

The Maya made a habit of writing the date, as measured by the Long Count, on many of their inscriptions. For this reason, archaeologists can tell exactly when significant events happened in the Maya world. For example, we know the powerful city of Tikal was conquered by an alliance of the rival cities Caracol and Calakmul in A.D. 562. Tikal would prove victorious over the nearby city of Dos Pilas in the next century, in 672, only to be defeated five years later by La Corona, an ally of Calakmul. The coronations of new kings, as well as the end of k’atuns and other auspicious dates, were also recorded on stela.

The Maya sometimes noted dates in terms of their distance from another date. Some calculations using this form of notation appear to have been used to refer to events extraordinarily far back in the past. One date corresponds to an event some 90 million years before A.D. 761, another stretches back even further, to 400 million years.

Finds like these, writes archaeologist Clive Ruggles, reveal the broader significance of the Maya’s use of calendars. Creating such lengthy blocks of time, he says , allowed the Maya to conceive of history on a grand scale.


The evolution of the calendar how to use a calendar today

We know little about the details of timekeeping in prehistoric eras, but wherever we turn up records and artifacts, we usually discover that in every culture, some people were preoccupied with measuring and recording the passage of time. Ice-age hunters in Europe over 20,000 years ago scratched lines and gouged holes in sticks and bones, possibly counting the days between phases of the moon. Five thousand years ago, Sumerians in the Tigris-Euphrates valley in today’s Iraq had a calendar that divided the year into 30 day months, divided the day into 12 periods (each corresponding to 2 of our hours), and divided these periods into 30 parts (each like 4 of our minutes). We have no written records of Stonehenge, built over 4000 years ago in England, but its alignments show its purposes apparently included the determination of seasonal or celestial events, such as lunar eclipses, solstices and so on.

The earliest Egyptian calendar [Ref.] was based on the moon’s cycles, but later the Egyptians realized that the “Dog Star” in Canis Major, which we call Sirius, rose next to the sun every 365 days, about when the annual inundation of the Nile began. Based on this knowledge, they devised a 365 day calendar that seems to have begun around 3100 BCE (Before the Common Era), which thus seems to be one of the earliest years recorded in history.

The evolution of the calendar how to use a calendar todayThe evolution of the calendar how to use a calendar today

Before 2000 BCE, the Babylonians (in today’s Iraq) used a year of 12 alternating 29 day and 30 day lunar months, giving a 354 day year. In contrast, the Mayans of Central America relied not only on the Sun and Moon, but also the planet Venus, to establish 260 day and 365 day calendars. This culture and its related predecessors spread across Central America between 2600 BCE and 1500 CE, reaching their apex between 250 and 900 CE. They left celestial-cycle records indicating their belief that the creation of the world occurred in 3114 BCE. Their calendars later became portions of the great Aztec calendar stones. Our present civilization has adopted a 365 day solar calendar with a leap year occurring every fourth year (except century years not evenly divisible by 400).

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Experts share four tips for using the common tool for planning your days

The evolution of the calendar how to use a calendar today

Much of Corrine Starke’s day unfolds in the calendar function of Microsoft Outlook.

As the executive assistant for William Fulkerson, the executive vice president for Duke University Health System, Starke manages one of Duke’s busier schedules. Filled with appointments, meetings, phone calls and reminders, the Outlook calendar Starke manages is the blueprint for how her office works.

“I couldn’t function without it,” said Starke, who’s worked with Fulkerson for 14 years. “I couldn’t imagine trying to flip through papers to try and keep things in order with the level of meetings and materials that we have come through.”

Become an Outlook Expert

Duke Learning & Organization Development is offering the one-day Outlook Email and Calendar Basics course in February and August of 2020.

For many at Duke, the Outlook calendar helps us chart our days. It’s where meetings get scheduled, reminders are kept and events that define our work are recorded.

Srini Iyengar, who teaches a course on Microsoft Outlook for Duke’s Learning and Organization Development (L&OD), said that participants who use the system often are occasionally surprised by some simple tricks that can help them use it more efficiently.

“A lot of people will get excited and say, ‘I didn’t know you could do that,’” said Iyengar, senior technology partner for L&OD. “There are people that have used Outlook for a number of years just doing the basic things. They didn’t know about these things.”

Check out a few of the fun, simple ways you can get more out of your Outlook calendar.

Make Your Schedule ColorfulThe evolution of the calendar how to use a calendar today

One of the more popular bits of advice Iyengar passes along is the use of color coding for events. When creating an event, click on “Categorize” in the toolbar at the top of the email and select from a number of colors. You can also right click on an existing calendar item, scroll down to “Categorize,” and pick a color.

Using colors, customize your schedule so events such as phone calls, meetings or personal appointments are easily identifiable at a quick glance.

“I use the colors to bring things to our attention, I use it to flag things so you don’t miss them,” said Starke, the executive assistant.

Iyengar also uses different colors for items.

“Phone calls may be in one color, if I have a conference call, I may make it a different color,” Iyengar said. “I’m doing a report and I want to block my time off, then I use a different color.”

Keep Your Private Items PrivateThe evolution of the calendar how to use a calendar today

Allowing a collaborator to see your schedule is a handy way to coordinate meetings. But do you want your colleagues to see everything on your schedule? Perhaps not.

You can control what information gets seen by others on your calendar. If you have an item that you’d like to keep private, right-click on it and select “Private.” That way, others will see that you have an item on your schedule at that time, but they won’t be able to see what it is.

“In this day and age when we care very much about privacy, this is a smart thing to do, and people may not be aware you can do it,” said Debrah Suggs, an IT Analyst with Duke’s Office of Information Technology, who taught a Learn IT @ Lunch session last year that covered simple tech tricks such as this.

Get Specific with TimeThe evolution of the calendar how to use a calendar today

When creating calendar events, the default setting allows you to schedule events that stick to 30-minute increments in duration. But what if you have a call that you know will take only 15 minutes?

You have the option to create custom lengths of meetings and appointments by typing in your own start and end times instead of simply using the 30-minute options offered in the drop down lists.

When building a schedule, it’s important to build in buffers between appointments to account for travel or other last-minute preparations. Scheduling short 10 to 15 minute blocks of protected time for those needs can help your day run smoothly.

Be FlexibleThe evolution of the calendar how to use a calendar today

A handy time management trick used by many Outlook users is creating appointments on your calendar to work on solo projects such as administrative tasks or writing. This can help you claim the blocks of time you need to get important work done.

But what if you have some flexibility with that time and don’t want someone looking to schedule an important meeting to see it as blocked off? If you right click on the calendar item and select “Show As” and select “Free,” the item will stay visible on your schedule, but someone looking to schedule an appointment won’t see it.

“This way, you can use the calendar to portion off your time and stay organized, but if someone needs to schedule a meeting, they can see that time is available for them,” Suggs said. “Otherwise, people might try to schedule meeting with you, see that time blocked off and have to go several days into the future, not because you’re unavailable, but because you were being organized.”

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The Cosmic Calendar is a scale in which the 13.7 billion year lifespan of our universe is mapped onto a single year. This chronological arrangement was done by famous astronomer Carl Sagan. In this mapping, the Big Bang took place on January 1st at 12 a.m., while the present moment is 12 p.m. on December 31st.

The Sun is older than the Earth, but it’s difficult to comprehend the massive age difference. Saying that the Earth’s age is 4.5 billion years, while the Sun’s age is 4.6 billion years, doesn’t actually seem to express how large that gap really is! It’s difficult for humans to wrap their heads around such time intervals thanks to our puny lifespan of barely 100 years.

For example, if someone were to ask an 8-year-old kid how much older his elder sister is, he’d probably give the answer correctly as 4 or maybe 5 years between them. However, that age difference looks huge to his 8-year-old self. However, it might not seem like a big deal to him when he’s fifty and there is no observable different between his and his sister’s age.

Similarly, wouldn’t it be easier if we had the whole history of the Universe condensed down to a more relatable time scale so that we could actually appreciate the time differences between cosmological events?

The evolution of the calendar how to use a calendar today

Made almost Five thousand years ago but merely a blip in the cosmic time-scale.

What is the Cosmic Calendar?

The concept of the cosmic calendar was popularized by famous astronomer Carl Sagan to help people understand just how far apart on a time scale events in the Universe are. He chronologically arranged the 13.8 billion years of the Universe’s age into a single year. In this visualization, the Big Bang took place on January 1st at 12 a.m., while the present moment is 12 p.m. on December 31st. However, this doesn’t mean that the Universe is going to end in this final second; the scale just continues condensing itself to accommodate the increasing age of the cosmos.

Obviously the condensation of 13.8 billion years into 365 days causes calendar time to speed up – a lot! At this rate, there are 438 years per second, 1.58 million years per hour and 37.8 million years per day. In other words, an actual second is 13,812,768,000 times longer than a Cosmic Calendar second.

January 1: 13.8 billion years ago: Big Bang

The evolution of the calendar how to use a calendar today

An Artist’s rendition of The Big Bang

The Big Bang and the creation of the Universe occurred here, as determined using cosmic background radiation from the explosion. This is as far back as the Calendar can go. It is pointless to try to go any further.

January 22: 12.85 billion years ago: First Galaxies

After a billion years of pure energy moving across the cosmos, the first galaxies in the universe were formed. Gases began to come together and coalesce to form stars, which in turn began to cluster as a result of their own gravity.

March 16: 11 billion years ago: Milky Way

The Milky Way, our neighborhood, was finally born after a million-year process of stars coming together to live in tandem after the first galaxies were formed.

August 28: 4.57 billion years: Solar System

The evolution of the calendar how to use a calendar today

The Solar System as know it now.

Our Solar System was formed when the Sun came into existence. Looking at this, it is surprising to observe that the Sun, born in September, is still incredibly young when compared to the age of the Milky Way.

September 6: 4.54 billion years ago: Earth

The oldest rocks on Earth have been dated to be about 4.4 billion years old, which approximates Earth’s formation in the cosmic calendar just 4 days after the formation of the Solar System.

September 7: 4.53 billion years ago: Moon

Just one day after us, our loyal satellite was formed and has been orbiting the Earth ever since.

September 14: 4.1 billion years ago: Life on Earth

Remains of biotic life on Earth was found in 4.1 billion-year-old rocks. Most prominently, single-celled primitive bacteria signified the birth of life on the primordial Earth.

September 30: 3.8 billion years ago: Photosynthesis

This might be the most essential breakthrough for life, since it signified the direct use of the Sun’s light to produce oxygen necessary for carbon-based life forms. All the earlier forms of life utilized only the Earth’s resources, but without photosynthesis, the atmosphere of Earth couldn’t be filled with oxygen.

December 5: 0.8 billion years ago: Multi-cellular life

The evolution of the calendar how to use a calendar today

From single to multi-celled organisms

The evolutionary jump from primitive bacteria to multi-cellular organisms took a very long time, but is responsible for life on Earth as we know it. This interval of almost 3 months is even longer than the time it took the first galaxies to form.

December 20: 0.45 billion years ago: Land Plants

The Earth began its journey to become lush and green when life took its first step onto land. The world was then being populated by amphibians and reptiles.

December 25: 0.23 billion years ago: Dinosaurs

The evolution of the calendar how to use a calendar today

Dinosaurs ruled the earth 23 million years ago

It has only been 5 days on the cosmic calendar since dinosaurs roamed the Earth.

December 30: 0.065 billion years ago: Dinosaur Extinction

The Cretaceous extinction event when a meteorite hit Earth and decimated almost every form of life. The non-avian dinosaurs died out, paving the way for mammals to conquer the world.

What happened on December 31?

December 31, 12 a.m.: 40 million years ago: Dawn of the primates

Whatever we have heard about the history of mankind on Earth happened on December 31st of the cosmic calendar. This truly shows us the insignificance of our time spent here on Earth. The dinosaurs had roamed the Earth for 5 days, and we were still living in trees on the dawn of that final day. Humanity is quite literally a blip on this calendar, as everything that follows happened on the final day of the year. For more specificity, the time has been shown instead of the date.

14:24 hrs – Primitive Humans were born.

22:24 hrs – Stone tools were used by humans and fire was domesticated.

23:59 hrs and 48 seconds – The Pyramids were built by the Egyptians.

23:59 hrs and 54 seconds – Buddha was born and the Roman Empire was formed.

23:59 hrs and 55 seconds – Christ was born, which marked the beginning of the Roman calendar (0 AD).

23:59 hrs and 58 seconds – Christopher Columbus discovered America

23:59 hrs and 59 seconds – The world as we know it… with Justin Bieber in it.

In one of my last tutorials here, we learned how to apply time-intelligence in DAX to analyze the COVID-19 data that is provided by Johns Hopkins University. The focus so far was to provide correct calculations on a daily level or to smooth them using running averages here.

In today’s quick tutorial, you will learn how to add weekly-based calculations. You can download the pbix file from here to use as the base-line for this tutorial.

We will start by creating a calculated column in your Calendar table for the week number. Click on the Data view (The second icon on the left sidebar). In the Fields pane on the right sidebar, select the Calendar table and click New column under Table tools.

The evolution of the calendar how to use a calendar today

Enter the following expression in the formula bar:

This WEEKNUM function will return the week number (for more options to set the week number go here). For example, for the date of January 22, 2020, the week number will be 4 since that date is in the fourth week in 2020.

The evolution of the calendar how to use a calendar today

Now you can use this column in the X-axis of your visualizations and apply your measures.

When WEEKNUM is not enough

When you use the Week Number in the X-axis as illustrated in the top bar chart below, your audience may find it a bit difficult to translate a week number with the actual date. In this section, you will learn how to translate the week number to the first date of the week and use it as illustrated in the bottom bar chart below.

The evolution of the calendar how to use a calendar todayWhen Week Number is not enough. How do conver week numbers to dates of the first day of the week

Go to Table tools and click Calculated column. In the formula bar, enter the formula below.

Note: You may already have a Year column in your calendar table. It can help you if you build your own date hierarchy in Power BI (You would also need to include the Month column). But in this tutorial, we need the Year column to ensure that we calculate the week start date correctly.

Add another calculated column with this formula:

The evolution of the calendar how to use a calendar today

If you need to apply weeks’ end dates in your analysis, here is your modified DAX formula (We only changed the MIN to MAX):

Let’s explain the code fo the calculated column of Week Start Date. In its core, we apply a MIN on the Date column to get the earliest date that we have for all the records with the same Week Number and Year. To get to the necessary calculation you would need to modify the filter context in DAX to support the requirement in bold above.

Without CALCULATE, the formula MIN( ‘Calendar'[Date] ) will return the earliest date in the entire calendar table, because there is no filter context when you run calculated columns.

The formula CALCULATE ( MIN( ‘Calendar'[Date] ) ) will return the same date you have in each row since the row context is converted into a filter context that includes the selected date.

To modify the filter context in CALCULATE and get all the rows with the same week number and year, we apply the ALLEXCEPT function that will return all the raws in the Calendar table except Week Number and Year which will not be filtered. As a result, rows with different Week Number or Year values will not be included in the result. This operation will return to us the affected result. The MIN function will run only on all the rows in the table with the same Week Number and Year and return the first date of the week.

Note: ALLEXCEPT is a less common function in DAX than ALL. As a result, you may already know how to achieve the same Week Start Date by applying ALL as shown in the formula below, but the function below is not efficient as it will iterate over all the days in the Calendar table.

Now you have the Week Start Date as a calculated column. It’s time to format it as a date.

The evolution of the calendar how to use a calendar today

Now, when we have the Week Start Date column we can place it in the X-axis of our visuals and analyze our data by weeks. In one of my previous tutorials here on building the COVID-19 dashboard, we used Time Intelligence to calculate the daily new cases. Here is the equivalent measure that calculates the weekly new cases:

By applying the Weekly New Cases in conjunction with the Week Start Date column you can now analyze the weekly new cases of confirmed cases of COVID-19 by weeks and use the week dates instead of numbers.

The evolution of the calendar how to use a calendar today

I hope you found this tutorial useful. In my next blog post, we will continue our exploration of PDF import as started here.