Well... that all depends where you are.  Living in the Western World, it is often easy to forget that other people in other parts of the world do things completely differently than us, and one of those things is how they record time.  The following is offered just to keep a perspective on time.  And when you’re dealing with Time, it’s always a good idea to have a little Perspective.

The Christian Calendar

This is also known as the Gregorian calendar, which is based on the start of the Christian Era...  you know, BC –  Before Christ and AD – Ado Domini (in the Year of Our Lord – not After Death).  Or, if you want to be politically correct and generally recognize that there are other people in the world other than you, you can use BCE and CE – Before Common Era and Common Era.  Mostly because of international economics, this is the calendar used by the majority of the world on a daily basis. 

The Islamic Calendar

As the name implies, the Islamic calendar is used primarily in Islamic countries, such as those found in the Middle East and Northern Africa.  This is a calendar based on the cycles of the moon.  As such, it’s really not practical for things like planting crops, and is used primarily for religious and other official purposes.  It is indicated with the letters “AH,” which mean “After Hijra.”  The calendar is dated from the year 622 CE, when the Prophet Mohammad and his followers returned to Medina.  (Which countries use the Islamic calendar) Because the Islamic calendar is based on the moon, and because a lunar year is shorter than a solar year, you really can’t just subtract 622 years from the current Christian calendar and come out right.  For instance, as of March 5, 2020, the current Islamic year is 1441.  However, if you subtract 622 from 2020, you get 1398, which is only a 579 year difference, so you would be off by 42 years.  There are several programs on the Internet that will convert Islamic dates to other dating systems.  (Prayer Times)

The Jewish Calendar

The Jewish calendar blends both a solar calendar and a lunar calendar, with some years having 12 months and, occasionally, others having 13, so the years stay fairly consistent with the Christian calendar.  The current Jewish year is 5780 AM – ano mundi – in the year of the world. (Hebrew Calendar)  The calendar dates back to when Jews believe that God created the universe, a year that was arrived at by counting backwards in the Jewish Bible. (Jewish Calendar).  Once again, it’s probably best to use a converter when trying to arrive at the current Jewish year (or, conversely, the current Christian year).  (Jewish/Civil Date Converter)

The Buddhist Calendar

This is a calendar used for civil purposes primarily in Thailand, and in other places (such as Tibet) for religious purposes.  Like the Jewish calendar, it is a blend of both solar and lunar, so it keeps pace fairly well with the Christian calendar.  (Buddhist Calendar)  The Buddhist Era (BE) dates from 544 BCE, when the Buddha entered Paribbāna – complete Nirvana. (Simple Buddhist).  The current Buddhist year, as of March 2020, is 2563 BE.

The Saka Calendar

Until 1957, India used around thirty different calendars throughout the country, making it difficult to do... well, pretty much everything.  It was in 1957 that they converted the entire country to the Saka Era, which dates back to 57 BCE (more or less), when Salivahana became King.  (Das)  The current year in India is 1942 SE, which is roughly a 78 year difference between the Saka and Christian Eras.  However, it is probably still best to use a converter to be for sure.  (The Indian Calendar)

Ethiopian Calendar

As the name might imply, this calendar is used primarily in Ethiopia, but is also used to a degree in neighboring Eritrea.  Based on the Coptic calendar (which is used primarily in Egypt), there are thirteen months in the Ethiopian calendar, twelve with 30 days, and the thirteenth comprised of whatever is left over to make it equal to the Christian calendar. (1 Ethiopian Calendar)  The Coptic calendar is based on when they believe Jesus ascended into heaven, which is eight years earlier than other Christian calendars.  Therefore, the current year in Ethiopia, as of March 2020, is 2012.  Be careful, though, because their new year is in September. (2 Ethiopian Calendar)

Coptic Calendar

The Coptic calendar, used primarily in Egypt, is based on the ancient Egyptian calendar, but modified, like most other calendars, to make sense with reality, with twelve months of 30 days and a thirteenth month that varies between 6 and 7 days to keep it current with the world’s standard, the Christian calendar.  The Coptic calendar dates from 284 CE, when the Roman Emperor Diocletian came to power.  Diocletian was not a particularly nice guy, which is why the Coptics use the abbreviation AM for Anno Martyrdom, the Year of the Martyrs, which is not to be confused with the Jewish AM. (Coptic Calendar)  The current year in the Coptic calendar, as of March 2020, is 1736.  Like the Ethiopian calendar, the first of the year for the Coptic Calendar falls in September. (The Coptic Calendar of Martyrs)

Though by far not inclusive, those are some of the more prominent calendars that are still being used throughout the world.  There are others, though, that are no longer generally being used and are of interest only if you are doing historical research or you happen to collect old coins.  These include the Korean, Chinese, Javanese Aji Saka, and Fasli calendars.  Not included, as well, are those calendars used primarily for such things as holidays and religious observations, such as the Zoroastrian calendar (and, as some would argue, the Coptic calendar).