Truncated Julian Day Converter Free Information

Truncated Julian Day Converter

This converter requires the use of Javascript enabled and capable browsers. There are two converters in this script, the first converting from TJD to MM-DD-YYYY in the modern Gregorian calendar format. The second converts from the MM-DD-YYYY format to the TJD number. This converter is accurate from 1754 A.D. to current date. All entries are numeric; in the case of months, it is MM, with the MM being from 01 to 12. Days (DD) are from 01 to 31. Years are in the (YYYY) four digit format of the year, such as 1994. In the case of the Truncated Julian Date, insert the correct TJD in the (NNNNN) format. Make the required entry or entries and click on Convert. For Financial dates and legal dates, days between dates, days before a date or days after a date, day of the week for a given date in history, involving the last 2 centuries approximately, we suggest that you use our Julian to current day and date calculator. In this converter, we have avoided the "time of day" factor. If you have the need for that, you can use our calendar date to Julian date and time calculator or our calendar date and time From Julian date calculator.

Modified Julian Date, MJD, is a modification of the Julian Date that is routinely used by astronomers, geodesists, scientists, financiers, and even some historians. This dating convention, designed to facilitate simplified chronological calculations, numbers all days in consecutive fashion, beginning at a date sufficiently far into the past so as to precede the historical period. Julian Day Number is an integer counter of the days beginning at noon on January 1, 4713 B.C. (no, even though I may look like it, I was not there...), which is Julian Day Number 0. The Julian Date (as opposed to Julian Day) is the non-integer extension of the Day Number to include a real fraction of day, allowing a continuous time unit. MJD modifies this Julian Date in two ways. The MJD begins at midnight rather than noon (the .5 in the formula), in keeping with more standard conventions and modern representation of time. Secondly, for simplicity, the first two digits of the Julian Date are removed. This is because, for some three centuries following November 17, 1858, the Julian day lies between 2400000 and 2500000. The MJD drops those first "24" digits. Thus, we have as a formula for converting from JD to MJD, MJD = JD - 2400000.5. (You may wish to use our MJD converter.)

Truncated Julian Date, TJD, is a truncated form of MJD. The starting TJD point is midnight May 24, 1968 (Ahhh, I remember that night well...). Thus there are two formulae for calculating TJD. TJD = MJD - 40000, assuming you know the MJD. If you only know the JD, TJD = JD - 2440000.5. In both cases, MJD and TJD, it is generally used in integer form, representing the day only, not the day and time, though it is fully capable of both day and time unless expressed as an integer.


Required Data Entry
Truncated Julian Day (NNNNN)
Calculated Results


Required Data Entry
Month (MM)
Day (DD)
Year (YYYY)
Calculated Results
Truncated Julian Day
Updated 6.05.11

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