Julian Date Converter - CosmoWerx
$1.99 £1.12 1.59€

The Julian Date Converter for iPad gives the user a simple and quick way to convert between Coordinated Universal Time (UTC) in the Gregorian Calendar and the Julian Date as well as the following selection of additional epochs and time systems:

  • Local Apparent Sidereal Time for any longitude as input by user
  • Modified Julian Date
  • Reduced Julian Date
  • Truncated Julian Date (NIST and NASA)
  • Dublin Julian Day
  • Lilian Day Number
  • ANSI Date
  • Rata Die
  • GPS Time calculated from UTC Time
  • Unix Time
  • RAMSES Time
The Sidereal Time at the users present position (using iPad location services) or any given longitude is also shown.



The Julian date (JD), not to be confused with Julian year, is the number of days and fractions of a day since noon January 1, 4713 BC at Greenwich. The Modified Julian Date (MJD) has an offset of 2,400,000.5 days from the Julian Date and hence starts at mJulian Date Converteridnight November 17, 1858. The Julian Date is often used for scientific time measurement by the astronomy community and was introduced to provide a single system of dates that could be used when working with different calendars.