Other countries and some individual nations (ethnic peoples) use many different dating systems, some related to the movement of the sun called Solar Calendars, some related to the movement of the moon called Lunar Calendars, some related to the movement of both the sun and moon and these are called Lunisolar Calendars and finally there are mathematical calendars that are not related to the relative movement of the astronomical bodies at all but to an abstract idea.
The table below displays today's date, 2012-05-20, in the most popular calendric systems currently in use around the world. The data will change automatically at midnight UTC (You may need to refresh your browser at that time). See the notes below this table for a brief explanation of the calendar systems that are displayed here.
| Calendar Name | Day Name | Local Day Name | Day Number | Month Name | Local Month Name | Month Number | Year |
|---|---|---|---|---|---|---|---|
Julian Day |
|
| 2456067.5 |
|
|
|
|
Modified Julian Day |
|
| 56067 |
|
|
|
|
Gregorian Calendar | Sunday |
| 20 | May |
| 5 | 2012 |
Hijri Lunar Calendar | al-Ahad | الأحد | 29 | Jumada II | جمادى الثانية | 6 | 1433 |
Indian Civil Calendar | Ravi vāsara | रविवासर | 30 | Vaishākha | वैशाख | 2 | 1934 |
Persian Calendar | Yek shanbeh | یک شنبه | 31 | Ordibehesht | اردیبهشت | 2 | 1391 |
Hebrew Calendar | Yom Rishon | יום ראשון | 28 | Lyar | אייר | 2 | 5772 |
Chinese Calendar | zhōurì | 周日 | 30 | Méiyuè | 梅月 | 4 | 4709 |
|
Chinese Year |
rénchén (壬辰) - Year of the Water Dragon |
(Jiazi sequence: 29) |
|||||
It is very difficult, but not impossible, to relate different calendars to one another. To do so one would have to continuously calculate to the fraction of a second as the day begins at different times in different calendars and also to users in different locations. Perhaps one day we will "give it a bash" and have a go creating the required code but until then we display the relationships between calendars to the nearest day based on UTC and a user located on the Greenwich Meridian. This means that the accuracy of the relationship is +/- 24 hours depending upon where you are!
The Julian Day number is the interval of time that has elapsed in days and fractions of a day since January 1, 4713 BC Greenwich noon (UTC). Although recording time in Julian Days has been around since Julius Caesar introduced it in 46BC the current scheme was proposed by Joseph Scaliger in the 16th Century and refined by the astronomer John Herschel in the late 19th Century. Julian Day Numbers have since become adopted by the scientific community for recording dates especially those regarding astronomical events. For the sake of simplicity in the modern era we knock off the first two numbers and ignore the decimal point to end up with the Modified Julian Day number.
Introduced by Pope Gregory XIII in 1582, the Gregorian Calendar has become the most widely used system for recording and communicating dates. It is the official state calendar system for most countries of the world although many also use additional calendar systems especially to calculate religious and cultural events.
The Hijri Lunar Calendar, or more commonly known as the Muslim or Islamic Calendar, is a true Lunar calendar but one based on astronomical observation rather than calculation. A new month commences when the New Moon is actually viewed by the observer just after sunset or if it was cloudy when the old month expires. This means that the month starts at different times at different places or rather different longitudes and explains why the month can be different in another country, It is common for Islamic countries to make their own observation and determination of the calendar on a month by month basis.
The Chinese Calendar is a Lunisolar calendar combining data from observations of both the sun and the moon. The calendar has been in use for nearly four thousand years and during this period was adopted by many of China's neighbours. The Chinese Calendar is used to determine the dates of religious and cultural events in much of Asia.
The are numerous calendars in use on the Indian sub-continent in fact so many that in 1957 the Indian Government introduced the Indian National Calendar, or Indian Civil Calendar, for official use and in the recording of state activities. Many of the other calendars, including the Hindu, Bengali, Nepali and Tamil calendars are still used to determine the dates of religious events but they must not be confused with the civil calendar.
The Persian Calendar or Solar Hejri calendar is also an ancient calendric system which is still in common usage in both Iran and Afghanistan. The calendar is not only used to determine religious holy days but also in general daily public use.
The Hebrew Calendar is used all over the world to determine the activities of the Jewish faith and in Israel as the official state calendar. it is a Lunisolar calendar.
The rising and setting sun probably became the human race's first calendar. The sun is excellent for telling us whether it is day or night but to the observer it does not change much over a long period. However as the primary source of energy for the world it has the greatest effect on the seasons and the agricultural growing cycle so it cannot be ignored whatever system is used.
As a time keeping device the moon is as useful as the sun and in some respects more so as it provides greater variation over shorter period of time. The moon has long been used by many of the world's ancient religions, such as Islam and Buddhism, to determine the date of their holy days and festivals. The Christian religion determines the date of Easter and its associated holy days from observation of the location of the moon. Using the moon to mark time over a longer period of time has its drawbacks as seasons determined from its movement 'drift' over time.
This is the most useful calendar in general use as it provides the benefits of both solar and lunar calendars and uses these benefits to reduce the impact of the disadvantages to the user. The Gregorian Calendar in general official use by all countries of the world as an adjusted lunisolar calendar.