TimeDeck

Julian Date Converter

Convert between calendar dates and Julian Day Numbers.

Today's Julian Date

2461140

Modified Julian Date: 61139.5

Select a calendar date and click Convert to get its Julian Day Number.

Julian Date System vs. Julian Calendar

The Julian Day Number (JDN) is a continuous count of days since the beginning of the Julian Period on January 1, 4713 BC (Julian calendar). It is widely used in astronomy, chronology, and software to avoid ambiguity between different calendar systems.

The Modified Julian Date (MJD) equals JDN minus 2,400,000.5. It starts at midnight rather than noon and uses smaller numbers, making it more convenient for modern use.

Do not confuse the Julian Date system with the Julian calendar, which was introduced by Julius Caesar in 46 BC and was later replaced by the Gregorian calendar in 1582. The Julian Day numbering system was proposed by Joseph Scaliger in 1583 and is unrelated to the calendar reform.

Notable Julian Day Numbers
JDNDescription
0January 1, 4713 BC (Julian calendar) -- JDN epoch
2299161October 15, 1582 -- Gregorian calendar adoption
2440000May 23, 1968 -- Modified Julian Date epoch
2440587.5January 1, 1970 -- Unix epoch

Disclaimer: The results provided by these calculators are estimates for informational purposes only and do not constitute financial, tax, or legal advice. Tax laws vary by jurisdiction and change frequently. Please consult a qualified accountant or tax professional before making financial decisions.

Frequently Asked Questions

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