Returns the number of seconds since January 1st, 1970, Midnight, in Greenwich (GMT). Also known as "Unix time", "timestamp" or "epoch".
Example:
clock seconds
on Dec 10 2004, 11:44:22, returns
1102686262
See also: clock
LV Is the epoch the same on all platforms and operating systems?
MSW Due to the source, at least under unix and windows the epoch is 1970-01-01 @ midnight. Under mac the epoch starts (due to the comments) Midnight Jan 1, 1904. mac/tclMacTime.c adds another tcl_mac_epoch_offset which is initialized by _mac_msl_epoch_offset_ if defined (and 0 otherwise), which I assume brings the Mac epoch in sync with the unix epoch. (I don't have a Mac handy to test...)
Lars H: It's better to say 00:00 than midnight, since each day also has a midnight at 24:00. But there is also another ambiguity, with respect to the time zone. When I do [clock format 0] I get Thu Jan 01 01:00:00 CET 1970, which seems to indicate that the epoch is from 1970-01-01 T 00:00 Z (i.e., it's the UTC/GMT midnight). Is this true on all platforms which use the 1970 epoch?
FPX Anybody knows the difference between Unix and Macintosh epoch? I was stumbling about this recently, requiring a platform-independent "seconds since epoch" value. Seems like the best we can do is
set sse [clock seconds]
if {[string equal $::tcl_platform(platform) "macintosh"]} {
incr sse <seconds between 1904 1970>
}Is the constant simply (negative) 2082844800, i.e., 60*60*24*(365*66+17), 66 years with 17 leap years, or do we also have to factor in some number of leap seconds?
Lars H: Alpha does the following [L1 ]:
# Convert seconds from 'epoch' to the unix epoch (used by 'clock').
proc ISOTime::fromEpoch {epoch when} {
global ISOTime::systemEpoch
if {$epoch == ""} {
set epoch [set ISOTime::systemEpoch]
}
if {$epoch == "unix"} {
return $when
} elseif {$epoch == "mac"} {
set when [expr $when + [clock scan "1904-01-01Z00:00:00"]]
return [expr $when - [ISOTime::ZoneOffset $when "unix"]]
} else {
error "ISOTime error: Unknown epoch \"$epoch\""
}
}Anyway the problem of the mac epoch is 2004 getting rather academic.
RS: Find out what your epoch is, without timezone offset, with
clock format 0 -gmt 1