# 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, allowing for more precise handling of fractional seconds.

To use one of these alternate systems you have to change the value of System Variable @DSP. Further, this value is saved into the project and therefore you must set a value for every project in which you wish to use an alternate date-time system.

Value of @DSP 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
 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. @DSP=value

@DSP supports three options

• 0 = Origin's long-time adjusted Julian Day system with "zero" at midnight on January 1, 4713 BCE (12 hours later than true Julian Day).
• 1 = True Julian Day ("zero" is January 1, 4713, BCE at 12:00 GMT).
• 2018 = 2018 date system, where "zero" is Jan 1 2018 00:00.
 Note: When @DSP is set as 1 and you want to display date data as time, we suggest set the Column Properties as shown below. Otherwise there will be offset of 12 hours.

### Converting Between Unix Timestamp and Julian Date

Depending on your version of Origin, there are a couple of ways to convert between a Unix timestamp and a Julian Date: