Julian Date Converter
Convert astronomical Julian Date or Modified Julian Date to a Gregorian UTC date/time, or calculate JD and MJD from a date.
Starts with an editable example. Replace the dates and rules with your own.
Your calculation
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Choose your dates.
Select your counting rules and calculate.
Calculation details
| Step | Value |
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How to use this calculator
Select JD or MJD and a direction. Enter a decimal day number or a Gregorian date/time in nominal UTC.
JD starts at noon and MJD equals JD minus 2400000.5. This converter uses 86,400-second days and Gregorian years 0001-9999, with millisecond calendar output. It does not convert between astronomical time scales.
A worked example
JD 2451545.0 corresponds to January 1, 2000 at 12:00 UTC in this nominal-day convention.
Is Julian Date the same as a Julian calendar date?
No. Julian Date is a continuous day count. The Julian/Gregorian calendar converter handles calendar month and day labels.
Which calendar and years are supported?
Each result states its calendar, time scale, precision and supported range. Batch converters accept up to 100 nonempty input lines and retain invalid rows. Copy, CSV and print include the calculation rules. Calendar downloads appear when a result contains dated events. Calculations run in your browser; no reminders or jobs are scheduled.
What happens to my dates?
Calculations run on your device. Saving a calculation is optional and keeps it in this browser. A setup link contains the dates and settings you entered; anyone with the link can read them. Use one tab per saved calculator. Clear saved data from Privacy & settings.