gives a date object corresponding to the Julian date jd.


gives a date object corresponding to the specified Julian date variant.

Details and Options

  • Julian dates, also known as Julian days or Julian day numbers, are extensively used to measure time in astronomy.
  • The Julian date jd is given as a number of days since noon January 1, -4713 in the proleptic Julian calendar, or November 24, -4714 in the proleptic Gregorian calendar, using the GMT time zone.
  • Possible Julian date variants include:
  • "Reduced"relative to noon on November 16, 1858
    "Modified"relative to midnight on November 17, 1858 (MJD)
    "Truncated"relative to midnight on May 24, 1968 (TJD)
    "Dublin"relative to noon on December 31, 1899 (DJD)
    "Full"relative to noon on November 24, 4714 BCE (JD)
  • The default Julian date variant used is "Full". All referenced dates are using the proleptic Gregorian calendar.
  • FromJulianDate returns a DateObject expression using the proleptic Gregorian calendar.
  • The following options can be given:
  • CalendarType Automaticcalendar system being used
    DateFormat Automaticformat used to display date
    DateGranularity Automaticcalendar granularity for the date
    TimeSystem "SmearedUTC"time system being used
    TimeZone Automatictime zone being used
  • Input Julian dates are assumed to be given in the time system specified by the TimeSystem option. The output DateObject expression will use the same time system.
  • Julian dates cannot denote the addition of leap seconds and therefore TimeSystem"UTC" is equivalent to TimeSystem"SmearedUTC" in input in the function FromJulianDate.


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Basic Examples  (2)

Create a DateObject from a Julian date specification:

Julian date variants have different epoch dates:

Options  (6)

CalendarType  (1)

By default, dates are generated as Gregorian calendar dates:

Use CalendarType"Julian" to generate an object with the "Julian" calendar:

DateFormat  (2)

Use long date format:

Specify your own format:

DateGranularity  (1)

By default, dates are generated with "Instant" granularity:

Use DateGranularity"Day" to generate a day granular date:

TimeZone  (1)

Specify the output TimeZone for the DateObject:

TimeSystem  (1)

Specify the time system of the Julian date:

The difference can be more than one minute for recent dates:

Properties & Relations  (5)

Integer Julian dates correspond to GMT noon:

By default, FromJulianDate returns results in your $TimeZone:

For a historical value of a time stamp in a given location at a given time, LocalTime can be used:

JulianDate[date] converts date into Julian date format:

FromJulianDate converts from Julian date format into a DateObject expression:

Julian dates can also be converted into DateObject expressions using the "JulianDate" calendar:

Convert to the Gregorian calendar:

On a day with a leap second, an integer input gives noon in the default "SmearedUTC" time system:

The middle point of the day is half a second after 12:00:00 in the "UTC" time system:

Wolfram Research (2015), FromJulianDate, Wolfram Language function, (updated 2023).


Wolfram Research (2015), FromJulianDate, Wolfram Language function, (updated 2023).


Wolfram Language. 2015. "FromJulianDate." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2023.


Wolfram Language. (2015). FromJulianDate. Wolfram Language & System Documentation Center. Retrieved from


@misc{reference.wolfram_2024_fromjuliandate, author="Wolfram Research", title="{FromJulianDate}", year="2023", howpublished="\url{}", note=[Accessed: 19-July-2024 ]}


@online{reference.wolfram_2024_fromjuliandate, organization={Wolfram Research}, title={FromJulianDate}, year={2023}, url={}, note=[Accessed: 19-July-2024 ]}