Modified Julian Date Converter
Convert a Modified Julian Date
MJD — the Julian date with 2,400,000.5 taken off, so it starts at midnight and fits in five digits. Used in satellite tracking, geodesy and time metrology.
Questions people ask
The things that come up about modified julian date converters, answered plainly.
Why does MJD exist?
Two reasons, both practical: subtracting 2,400,000.5 shifts the day boundary to midnight, and it drops the value to five digits — which mattered a great deal when it was invented in 1957 for satellite tracking on machines with small words.
What is MJD today?
Around 60,900 in mid-2025. MJD 0 was 17 November 1858, which is the zero point you get from that particular subtraction rather than any historical event.
Related tools
Julian days, Excel serials, GPS time, cron expressions and format validators.
Julian Date ConverterThe astronomer's continuous day count, both ways — including the half-day offset that catches everyone, since a Julian day begins at noon rather than midnight.
Julian Day Number CalculatorThe whole-number form — the JD of the noon that starts a day — with the Lilian and Rata Die day counts beside it, which are the same idea from different zero points.
GPS Time ConverterGPS seconds, week number and time-of-week, converted with the leap-second offset applied — because GPS time has taken none since 1980 and is now 18 seconds ahead of UTC.
Epoch ConverterThe same conversion as a Unix timestamp, plus the other epochs a number might belong to — Windows FILETIME, .NET ticks, Excel serials, Julian days — ranked by how plausible each reading is.