Dates & time
Julian date converter
Translate UTC calendar date-times and astronomical Julian dates.
A clear answer. Here’s how.
Uses JD = Unix milliseconds/86,400,000 + 2,440,587.5, with noon as the integer-day boundary. Modified Julian Date = JD − 2,400,000.5. Dates use the proleptic Gregorian calendar and UTC labels with fixed 86,400-second days; no historical calendar switch, leap-second, UT1 or TT correction is applied. Reverse output rounds to the nearest millisecond.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Direction
- UTC calendar → Julian date
- UTC date-time (YYYY-MM-DDTHH:MM:SSZ)
- 2000-01-01T12:00:00Z
Example result
- UTC calendar date-time
- 2000-01-01T12:00:00.000Z
- Julian date (UTC convention)
- 2,451,545
- Modified Julian Date
- 51,544.5
Proleptic Gregorian dates and fixed 86,400-second days. No leap-second or time-scale correction.