This website allows you to interconvert dates from Gregorian calendar, Hebrew calendar, Islamic calendar and Julian calendar and Day.
The Gregorian calendar is the most widely used calendar in the world. It is a solar calendarproclaimed by Pope Gregory XIII and took effect in 1582, in which October 4, 1582 of the Julian calendar was followed by October 15 in the new calendar, correcting for the accumulated discrepancy between the Julian calendar and the equinox as of that date. Common Era or Current Era, abbreviated CE is a calendar era that is used as an alternative naming of the Anno Domini era ("in the year of the Lord"), abbreviated A.D.
Julian Day is useful for scientists, astronomers and computer programmers because it is easier to do arithmetic with dates. It starts at noon on Monday, 1st January of year 4713 B.C.E. in the Julian calendar because in 1583 astronomer and historiaan named Scaliger considered it was that day the origin of history. In 1849 great astronomer Herschel considered that day Julian Day 0 and count day numbers from that day.
Julian Day (MJD) is created by subtracting 2400000.5
from a Julian day number, and thus represents the number of
days elapsed since midnight (00:00) Universal Time on
November 17, 1858. Modified Julian Days are widely used to
specify the epoch in tables of orbital elements of
artificial Earth satellites. Since no such objects existed
prior to October 4, 1957, all satellite-related MJDs are
The Julian calendar was proclaimed by Julius Caesar in 46 B.C.
and underwent several modifications before reaching its final
form in 8 C.E. The Julian calendar differs from the Gregorian
only in the determination of leap years, lacking the correction
for years divisible by 100 and 400 in the Gregorian calendar.
In the Julian calendar, any positive year is a leap year if
divisible by 4. (Negative years are leap years if when
divided by 4 a remainder of 3 results.) Days are considered to
begin at midnight.
In the Julian calendar the average year has a length of 365.25 days.
compared to the actual solar tropical year
of 365.24219878 days. The calendar thus accumulates one day of
error with respect to the solar year every 128 years.
Being a purely solar calendar, no attempt is made to synchronise the
start of months to the phases of the Moon.
The Hebrew (or Jewish) calendar is a lunisolar calendar. It attempts to simultaneously maintain alignment between seasons and the Sun and to synchronise months with the Moon. Days are defined as beginning at sunset, and the calendar begins at sunset the night before Monday, October 7, 3761 B.C.E. in the Julian calendar, or Julian day 347995.5. An hour is 1/12 of the time from sunrise to sunset. Weekdays start with Sunday followed by Saturday (Shabbat). Months corresponds to zodiac constellations. Maimonides established in March 22, 1178 C.E. established that year was 4938 of the creation of the world. They called their calendar Anno Mundi A.M. AM 5777 began at sunset on 2 October 2016 C.E.
The Islamic calendar is purely lunar and consists of twelve alternating
months of 30 and 29 days, with the final 29 day month extended to
30 days during leap years. The calendar begins
on Friday, July 16th, 622 C.E. in the Julian calendar, Julian
day 1948439.5, the day of Muhammad's flight from Mecca to Medina,
with sunset on the preceding day reckoned as the first day of
the first month of year 1 A.H.--"Anno Hegira"--the Arabic word
for "separate" or "go away". Days begin at sunset, weeks begin on Sunday, and the
names for the days are just their numbers: Sunday is the first
day and Saturday the seventh. Months starts in crescent moon.
There are many other calendars: Chinese, Persian, Indian, etc. Do a research and try to convert dates with your own code.