Julian Date to calendar date
For example, 2460000.5 is Sat, Feb 25, 2023, 12:00:00 AM UTC, which is 2023-02-25T00:00:00.000Z in ISO 8601 and 1677283200 in Unix seconds.
Julian Date: days since noon UTC on 1 January 4713 BC, so a fraction of .5 is midnight. JD 2440587.5 is the Unix epoch. Values of 1,000,000 or more are read as JD; write MJD in front to force a Modified Julian Date.
Detected: Julian Date (JD)/t/2460000.5
Your timezone
UTC · GMT+00:00 · UTC
Sat, Feb 25, 2023, 12:00:00 AM
Common formats
UTC
Sat, Feb 25, 2023, 12:00:00 AM
ISO 8601
2023-02-25T00:00:00.000Z
Unix (seconds)
1677283200
Unix (millis)
1677283200000
Relative
…
A Julian Date (JD) counts days since noon UTC on 1 January 4713 BC, fraction included, so astronomers can subtract two instants without touching a calendar. The Modified Julian Date (MJD) is JD minus 2400000.5, which moves the zero to midnight on 17 November 1858 and keeps the number short. Paste either below. Values of a million or more are read as JD and smaller ones as MJD; write JD or MJD in front of the number to force a reading.
Do it with the API
curl https://parsetime.dev/api/t/2460000.5?format=julian-dayThe same conversion as JSON: no key, no signup, permissive CORS. Try this call or read the API docs.
Common questions
- How do I convert a Julian Date to a Unix timestamp?
- Unix seconds = (JD − 2440587.5) × 86400, because JD 2440587.5 is midnight UTC on 1 January 1970. For an MJD, add 2400000.5 first, or use Unix seconds = (MJD − 40587) × 86400.
- What is the difference between JD and MJD?
- MJD = JD − 2400000.5. The subtraction drops the leading 24 and moves the day boundary from noon to midnight UTC, so MJD 60000 is the whole of 25 February 2023 while JD 2460000 starts at noon on 24 February. This page reads values of 1,000,000 or more as JD and smaller values as MJD; a JD or MJD prefix overrides that.
- Why does a Julian Date change at noon?
- Astronomers chose a noon epoch so that one night of observations falls inside a single Julian day. The .5 in 2440587.5 is that half day between the JD noon boundary and the Unix midnight epoch.
- Can I convert a Julian Date with the API?
- Yes: GET /api/t/2460000.5?format=julian-day returns the decoded date as JSON, with no key or signup. Prefix the value, as in /api/t/MJD60000?format=julian-day, to force the modified reading.