Tools: Julian Date Converter

	Today's date is 25-Apr-2024 (UTC). Today's Julian Date is 24116 . Convert Date or Julian Date:

Notes About Julian Dates

We refer to a yyddd date format (yy = year, ddd=day) as a 'Julian Date' - this is the common term for such a date in mainframe and other circles. However technically, a Julian date can mean different things. Astronomers refer to a Julian date as the number of days since the beginning of the Julian Period (January 1, 4713 BC). The Smithsonian Astrophysical Observatory introduced the 'Modified Julian Date' to record the orbit of the Sputnik satellite in 18 bits.

A yyddd (or similar format such as yyyyddd, yy-ddd) date is more correctly called an ordinal date. However in the mainframe world, we call them 'Julian Dates', and so we've used this term on this page.

Instructions:

Use this tool to convert between date and Julian (yyddd) date formats.

Enter a valid date or Julian date, and click 'Convert'. To see an example, click 'Show Example'.

Enter dates in the form mm/dd/yy, dd-mmm-yyyy, 'today', '+1 day' or similar. Enter Julian dates in the format yyddd, yy-ddd or yy.ddd

Remember:

• This tool can only convert date values after Jan 1, 1970.