2012

DATE
Quick Reference
See also:
■ Obtain General Drawing Information
(Read-only)
RealType:
Not-savedSaved in:
VariesInitial value:
Stores the current date and time in Modified Julian Date format.
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 DATE. To extract the seconds since midnight from the value
returned by DATE, use AutoLISP expressions:
(setq s (getvar "DATE"))
(setq seconds (* 86400.0 (- s (fix s))))
Because your computer clock provides the date and time, the DATE system
variable returns a true Julian date only if the system clock is set to UTC/Zulu
(Greenwich Mean Time). TDCREATE and TDUPDATE have the same format
as DATE, but their values represent the creation time and last update time of
the current drawing.
2218 | Chapter 31 D System Variables