# 2.1.13 Dates and Times in Origin

Origin interprets dates based upon the Gregorian Calendar. Time is interpreted in hours:minutes:seconds. Origin supports the following date ranges:

• When entering four digits for the year, Origin supports a date range of:
1/1/0100 to 12/31/9999.
• When entering two digits for the year, Origin supports a date range of:
0 to 44 = 2000 to 2044
45 to 99 = 1945 to 1999

### Origin's Mathematical System for Date and Time

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 "time zero" (t0). However, Origin's system differs in employing a 12 hour offset (see next).

#### Origin's Default System: Adjusted Julian Date

Origin's long-time, default date-time system establishes t0 as January 1, 4713 BCE (January 1, 4713 24:00:00 BCE or January 2, 4713 00:00:00 BCE) -- 12 hours later than the standard Julian t0 value.

In this system, Origin interprets a calendar date+time of ...

11 June 1998 at 21:23:01

... as a date value of ...

2450975.890984.

To obtain a true astronomical Julian Date value, you must add 0.5 to Origin's value (0.5 days = 12 hours), yielding a value of 2450976.390984.

No assumptions are made about time zones or any time shifting scheme (such as Daylight Savings).

#### Alternate Date-Time Systems in Origin

Starting with Origin 2019, Origin offers two alternate date-time systems - a true Julian Date system and a "2018" system in which t0 is defined as January 1, 2018 at 00:00.

To choose an alternate system, you must change the value of System Variable @DS:

Value of @DS Calendar Date Internal Numeric Comments
0 2018-07-26 13:35:00 2458325 .56597222 Origin’s long-time default (True Julian Date – 0.5)
1 2018-07-26 13:35:00 2458326 .06597222 True Julian Date
2018 2018-07-26 13:35:00 206 .565972222222 t0 = Jan 1 2018 00:00

The @DS system variable is what is termed a "persistent" system variable, meaning that changes to the value of this variable are written to the Windows registry and read upon startup.

 Origin's "2018" system allows for greater numeric precision when working with measurements made to fractions of a second. When working with contemporary dates, calculations involving measurements to 10-8 seconds can be supported.

To choose an alternate default date-time system for your Origin software:

1. Run Origin and from the main menu, choose Window: Script Window (Shift+Alt+3).
2. In the Script Window, type the following (choosing a value from the above table), the press Enter.
3. @DS=value
4. Restart Origin for your change to take effect.

#### Applying Alternate Date-Time Systems to Origin Projects

You can apply an alternate date-time system to the Origin project. You may be concerned with this if, for instance, you are sharing your projects with other Origin users and you do not know which date-time system they are currently using.

• Set a date-time system for the project using the system variable @DSP.
• By default, the date-time system stored with the project is the current Origin software default (e.g. if @DS=2018, then @DSP=2018).
• You can set @DSP to a different value and save the project, the new value of @DSP is saved with the project. When the project is closed, the value of @DSP reverts to that of @DS.
• If you reopen the saved project, you will see that the value of @DSP reverts to that of the current project.

To save a particular date-time system with your Origin project:

1. Run Origin and from the main menu, choose Window: Script Window (Shift+Alt+3).
2. In the Script Window, type the following (choosing a value 0,1 or 2018), the press Enter.
3. @DSP=value
4. Save the Origin project.