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to the \fBclock add\fR command. The result is interpreted as
a nominal number of seconds from the Epoch.
.PP
Surprising results
may be obtained when crossing a point at which a leap second is
inserted or removed; the \fBclock add\fR command simply ignores
leap seconds and therefore assumes that times come in sequence,
23:59:58, 23:59:59, 00:00:00. (This assumption is handled by
the fact that Tcl's model of time reacts to leap seconds by speeding
or slowing the clock by a minuscule amount until Tcl's time
is back in step with the world.
.PP
The fact that adding and subtracting hours is defined in terms of
absolute time means that it will add fixed amounts of time in time zones
that observe summer time (Daylight Saving Time). For example,
the following code sets the value of \fBx\fR to \fB04:00:00\fR because
the clock has changed in the interval in question.
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to the \fBclock add\fR command. The result is interpreted as
a nominal number of seconds from the Epoch.
.PP
Surprising results
may be obtained when crossing a point at which a leap second is
inserted or removed; the \fBclock add\fR command simply ignores
leap seconds and therefore assumes that times come in sequence,
23:59:58, 23:59:59, 00:00:00. This assumption is handled by
the fact that Tcl's model of time reacts to leap seconds by speeding
or slowing the clock by a miniscule amount until Tcl's time
is back in step with the world.
.PP
The fact that adding and subtracting hours is defined in terms of
absolute time means that it will add fixed amounts of time in time zones
that observe summer time (Daylight Saving Time). For example,
the following code sets the value of \fBx\fR to \fB04:00:00\fR because
the clock has changed in the interval in question.
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