UsefulVerse
Language · English

Free to use, no account

Julian Date Converter

Convert a Gregorian UTC date and time to Julian Date and Modified Julian Date, or turn a JD/MJD value back into UTC. This lightweight calculator runs locally in your browser.

Uses the proleptic Gregorian calendar and UTC, with no leap-second representation. JD begins at noon; MJD = JD − 2,400,000.5. Reverse conversion is rounded to the nearest millisecond. Supported years: 0001–9999.

How do I convert a UTC date to Julian Date?

Choose a conversion direction, enter a UTC date and time or a JD/MJD value, then convert. The result states UTC, the proleptic Gregorian calendar and millisecond output precision.

Frequently asked questions

How do I convert a UTC date to Julian Date?

Choose a conversion direction, enter a UTC date and time or a JD/MJD value, then convert. The result states UTC, the proleptic Gregorian calendar and millisecond output precision.

Is my date sent to a server?

No. The conversion runs in this browser. No date is uploaded or saved by this tool.

What is the Julian Date at the J2000 epoch?

For 2000-01-01 12:00 UTC, this converter returns JD 2451545 and MJD 51544.5.

What is the difference between JD and MJD?

Modified Julian Date is calculated as MJD = JD − 2400000.5. This shifts the day boundary to midnight and gives smaller values.

Does this converter handle leap seconds or local time zones?

No. Enter UTC. Leap seconds are not represented; the tool uses ordinary Gregorian calendar dates and UTC clock time.