Origin interprets dates based upon the Gregorian Calendar. Time is interpreted in hours:minutes:seconds. Origin supports the following date ranges:
Origin's mathematical system for date and time is based on the astronomical Julian Day, which defines January 1, -4712 (January 1, 4713 BCE), 12 hours Greenwich Mean Time as zero. Note that Origin uses a -12 hour offset in order to have 0 hours coincide with midnight. When you read the phrase Julian-date value in the Origin documentation, you should understand that this refers to Origin's value, which includes the -12 hour offset. No assumptions are made about time zones or any time shifting scheme (such as Daylight Savings).
In this system, for example, Origin interprets ...
... as a date value of ...
To obtain the astronomical Julian Date, we add 0.5 (to account for Origin's -12 hour offset), yielding a value of 2450976.390984.
For more information on Origin's Date and Time formats, see these topics:
Reference: Wikipedia contributors, "Julian day," Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/wiki/Julian_day.