I have heard conflicting stories about whether the time shift is
significant. Jeff Bisbee posted that systems based on UTC don't see
shifts in time() when DST/Standard arrive. Matt Cashner is convinced
that NTP prevents the problem from occurring.
the combination of those two ideas pretty much guarantee a time shift less system on a well maintained box. ntp will keep the system time from drifting more than a few attoseconds from standard. and utc doesn't change. the epoch time where $ENV{TZ} is set to UTC, GMT or one of the other synonyms will see no time shift around the daylight saving time jumps.
m.
