| (Read-only) | |
| Type: | Real |
| Saved in: | Drawing |
Stores the date and time that the current drawing was last saved. This value is represented as a Modified Julian Date (MJD), which is the Julian day number and decimal fraction of a day in the format
<Julian day number>.<Decimal fraction of a day>
The Modified Julian Date, conventionally called UT1, is a worldwide scientific standard that assigns day numbers beginning at an essentially arbitrary date and time of 12:00 a.m. on 1 January, 4713 B.C. (B.C.E.). With this system, 4 July, 1997 at 2:29:58 p.m. corresponds to 2450634.60387736 and 1 January, 1998 at 12:00 noon corresponds to 2450815.50000000.
You can compute differences in date and time by subtracting the numbers returned by TDUPDATE. To compute the seconds since midnight from the value returned by TDUPDATE, multiply the decimal fraction in TDUPDATE by 86400 seconds.
Since your computer clock provides the date and time, the TDUPDATE system variable returns a true Julian date only if the system clock is set to UTC/Zulu (Greenwich Mean Time).