Calendar Creation!!!
Start
Throughout this interactive experience, you will be able to create your ideal calendar. You will be faced with many different choices that will lead you down a wide variety of calendars seen throughout the history of the world. You will learn what factors led to the creation of these calendrical systems and why exactly they are so different.
Start
Option 1 (Base)
This decision is the most critical for creating a helpful and consistent calendrical system. Every useful and consistent calendrical system focuses on a certain cycle. There are 4 major ones: Solar, Lunar, Luni-solar, and Sidereal. Solar Calendar: Solar calendars are designed to stay consistent with the four seasons; doing so requires a deep understanding of the length of the tropical year. Lunar Calendar: Lunar calendars are built on the foundation of moon cycles. 12 moon cycles are seen throughout one solar year. Luni-Solar Calendar: The Luni-Solar calendar exhibits intercalation, which is the implementation of months in order to ensure accuracy.
Solar Calendar
Solar Calendars are designed to work with the tropical year so that the seasons stay consistent in the year. For this to be possible, you must know the length of the natural tropical year. The tropical year is 365.25 days, which created many issues due to a quarter of a day not being possible. Many civilizations found different solutions for this problem.
Lunar Calendar
Lunar Calendars are based on the moon phases. These calendars use a synodic month, which is about 29.53 days long. This is roughly the length of time it takes for the moon to complete its cycle from new moon to new moon again.
Luni-Solar Calendar
The Luni-Solar Calendar puts parts of the solar and lunar calendars together. It combines the lunar cycle with the solar year. This is done by including an intercalculation. This intercalculation is done to try to limit inaccuracies within the calendar, trying to keep to the most accurate time.
CONGRATS! You've just made the Egyptian Calendar!
The Egyptian calendar was very unique in the way time was determined. It was different from every other type of calendar with the fact that one week was ten days, three weeks were a month, four months were a season, and three seasons were a year.
CONGRATS! You've just made the Julian Calendar!
The Julian calendar had a very simple leap year. This simple system led to the need for constant fixing in order to stay aligned with the solar year.
CONGRATS! You've just made the Aztec Xiuhpohualli Calendar!
How else would you like to develop your calendar?
This calendar has a two hundred and sixty day cycle and was broken into units of twenty days. Each day has its own name, symbol, deity, and augury. These twenty-day units also ran simultaneously as a group of thirteen numbered days, meaning each day had a name and number, with the number changing as the calendar rotated.
CONGRATS!You've just made the Celtic Calendar!
What else would you like to do with your Calendar?
This calendar is split into halves: the dark and the light. The first half is called Samhain and was set to start on October 31st. The second half is called Bealtaine and begins on May 1st. A Celtic month started on a full moon rather than a new moon.
CONGRATS! You've just made the Sumerian Calendar!
What else would you like to do with your Calendar?
The Sumerian calendar was primarily Lunar. It's months were dependent on the moon phases. Each month began with the new moon. Their calendar had a significant focus on agricultural cycles, making it a crucial part of Sumerian communities.
Sumerian reform
Sumerian calendar over millenia reformed from lunar to solar which laid groundwork for julian calendar. They reworked their calendar to incorporate lunar months with solar alignment in order to keep seasonal events from drifting
Reform as Solar
CONGRATS!You've just made the Babylonian Calendar
What else would you like to do with your Calendar?
The Babylonian calendar was an intertwining of their understanding of time with agricultural cycles, religious observations, and daily life. This calendar was made of the moon, and its months began with sightings of the new moon.
CONGRATS! You've just made the Hebrew Calendar
The Hebrew mixes Lunar and Solar in the way that they make adjustments to resync the calendar. This adjustment is made through the addition of an extra month every couple of years.
A.1.b
Coptic Calendar
This calendar is divided into thirteen months. Twelve months have thirty days and the thirteenth month has five days.
Restart
A.2.a
Modern Gregorian calendar
The modern Gregorian Calendar refined the leap year system to make it so that the chance of error was greatly decreased. This calendar also skips ten days in October to properly realign it.
Restart
A.2.b
Julian calendar (old style)
The old Julian calendar has twelve months, seven of those months have thrity-one days. This calendar still has the issues with leap years and being misaligned with the solar year.
Restart
A.3.a
Oops your calendar died out
It seems like your calendar was replaced or completely discontinued, either due to small flaws making your calendar less accurate than others, or competing civilizations forcing the end of your calendar. Most calendars were replaced by the Julian and Gregorian calendrical systems for a variety of reasons. The most common reason is simply that the Roman Empire forced its calendar onto all of the civilizations they've conquered; with such a vast empire, its calendrical system became the most prominent calendar on the planet.
Restart
B.1.a
OOps your calendar has been replaced by the julian calendar
Perhaps it was a flaw in your calculations or one in your defenses that led to your calendar being replaced with the Julian Calendar. The Julian Calendar was more consistantly accurate than others which led it to be adopted by other cultures. Also, the Julian calendar was enforced onto every civilization under the Roman Empire, thus making it widely utilized across the world.
Continue?
C.2.a
Jewish religious calendar
The Jewish religious calendar is a lunisolar system that governs Jewish holidays, festivals, and daily observances. It combines lunar months with solar years, ensuring that holidays align with both moon phases and agricultural seasons
Restart
Calendar Creation!!!
Cameron Murphy
Created on October 28, 2025
Start designing with a free template
Discover more than 1500 professional designs like these:
View
Branching Scenario: Save Christmas
View
Branching Scenarios Challenge Mobile
View
Branching Scenario Mission: Innovating for the Future
View
Teaching Challenge: Transform Your Classroom
View
Branching Scenario: Academic Ethics and AI Use
View
Strategic Decisions: Branching Scenario
View
Branching Scenario: College Life
Explore all templates
Transcript
Calendar Creation!!!
Start
Throughout this interactive experience, you will be able to create your ideal calendar. You will be faced with many different choices that will lead you down a wide variety of calendars seen throughout the history of the world. You will learn what factors led to the creation of these calendrical systems and why exactly they are so different.
Start
Option 1 (Base)
This decision is the most critical for creating a helpful and consistent calendrical system. Every useful and consistent calendrical system focuses on a certain cycle. There are 4 major ones: Solar, Lunar, Luni-solar, and Sidereal. Solar Calendar: Solar calendars are designed to stay consistent with the four seasons; doing so requires a deep understanding of the length of the tropical year. Lunar Calendar: Lunar calendars are built on the foundation of moon cycles. 12 moon cycles are seen throughout one solar year. Luni-Solar Calendar: The Luni-Solar calendar exhibits intercalation, which is the implementation of months in order to ensure accuracy.
Solar Calendar
Solar Calendars are designed to work with the tropical year so that the seasons stay consistent in the year. For this to be possible, you must know the length of the natural tropical year. The tropical year is 365.25 days, which created many issues due to a quarter of a day not being possible. Many civilizations found different solutions for this problem.
Lunar Calendar
Lunar Calendars are based on the moon phases. These calendars use a synodic month, which is about 29.53 days long. This is roughly the length of time it takes for the moon to complete its cycle from new moon to new moon again.
Luni-Solar Calendar
The Luni-Solar Calendar puts parts of the solar and lunar calendars together. It combines the lunar cycle with the solar year. This is done by including an intercalculation. This intercalculation is done to try to limit inaccuracies within the calendar, trying to keep to the most accurate time.
CONGRATS! You've just made the Egyptian Calendar!
The Egyptian calendar was very unique in the way time was determined. It was different from every other type of calendar with the fact that one week was ten days, three weeks were a month, four months were a season, and three seasons were a year.
CONGRATS! You've just made the Julian Calendar!
The Julian calendar had a very simple leap year. This simple system led to the need for constant fixing in order to stay aligned with the solar year.
CONGRATS! You've just made the Aztec Xiuhpohualli Calendar!
How else would you like to develop your calendar?
This calendar has a two hundred and sixty day cycle and was broken into units of twenty days. Each day has its own name, symbol, deity, and augury. These twenty-day units also ran simultaneously as a group of thirteen numbered days, meaning each day had a name and number, with the number changing as the calendar rotated.
CONGRATS!You've just made the Celtic Calendar!
What else would you like to do with your Calendar?
This calendar is split into halves: the dark and the light. The first half is called Samhain and was set to start on October 31st. The second half is called Bealtaine and begins on May 1st. A Celtic month started on a full moon rather than a new moon.
CONGRATS! You've just made the Sumerian Calendar!
What else would you like to do with your Calendar?
The Sumerian calendar was primarily Lunar. It's months were dependent on the moon phases. Each month began with the new moon. Their calendar had a significant focus on agricultural cycles, making it a crucial part of Sumerian communities.
Sumerian reform
Sumerian calendar over millenia reformed from lunar to solar which laid groundwork for julian calendar. They reworked their calendar to incorporate lunar months with solar alignment in order to keep seasonal events from drifting
Reform as Solar
CONGRATS!You've just made the Babylonian Calendar
What else would you like to do with your Calendar?
The Babylonian calendar was an intertwining of their understanding of time with agricultural cycles, religious observations, and daily life. This calendar was made of the moon, and its months began with sightings of the new moon.
CONGRATS! You've just made the Hebrew Calendar
The Hebrew mixes Lunar and Solar in the way that they make adjustments to resync the calendar. This adjustment is made through the addition of an extra month every couple of years.
A.1.b
Coptic Calendar
This calendar is divided into thirteen months. Twelve months have thirty days and the thirteenth month has five days.
Restart
A.2.a
Modern Gregorian calendar
The modern Gregorian Calendar refined the leap year system to make it so that the chance of error was greatly decreased. This calendar also skips ten days in October to properly realign it.
Restart
A.2.b
Julian calendar (old style)
The old Julian calendar has twelve months, seven of those months have thrity-one days. This calendar still has the issues with leap years and being misaligned with the solar year.
Restart
A.3.a
Oops your calendar died out
It seems like your calendar was replaced or completely discontinued, either due to small flaws making your calendar less accurate than others, or competing civilizations forcing the end of your calendar. Most calendars were replaced by the Julian and Gregorian calendrical systems for a variety of reasons. The most common reason is simply that the Roman Empire forced its calendar onto all of the civilizations they've conquered; with such a vast empire, its calendrical system became the most prominent calendar on the planet.
Restart
B.1.a
OOps your calendar has been replaced by the julian calendar
Perhaps it was a flaw in your calculations or one in your defenses that led to your calendar being replaced with the Julian Calendar. The Julian Calendar was more consistantly accurate than others which led it to be adopted by other cultures. Also, the Julian calendar was enforced onto every civilization under the Roman Empire, thus making it widely utilized across the world.
Continue?
C.2.a
Jewish religious calendar
The Jewish religious calendar is a lunisolar system that governs Jewish holidays, festivals, and daily observances. It combines lunar months with solar years, ensuring that holidays align with both moon phases and agricultural seasons
Restart