<<After the recent daylight savings time change, and the ensuing
discussion about SETCLOCK and TimeZone variable, I'm just a little confused
(nothing new there!).  So, can anyone give me the "big picture" about how
SETCLOCK, the TZ variable, and SHOWTIME fit together?>>


SETCLOCK changes the system clock (DATE=, TIME=, CORRECTION=) or zone offset
(TIMEZONE=), and SHOWTIME displays the current values.

TZ is used by software that expects standards-based (that's as opposed to
MPE-unique) time-retrieval functions. Things line the C library functions
'localtime()' and 'ctime()'. It is necessary because these functions work
with structures that contain UTC values, and they ask the system for the UTC
offset to apply when they convert the UTC values to local times. TZ has been
around for many years in other systems, but it has just become more visible
on the majority of MPE systems in the last few years, as people use more and
more software ported from other environments. If you don't have a
system-wide logon UDC that sets TZ properly, you might want to create one.

        <<For instance, here is a display from my system:

        :SHOWCLOCK

        SYSTEM TIME: MON, APR  6, 1998, 10:02:26 PM
        CURRENT TIME CORRECTION:            0 SECONDS
        TIME ZONE:    4 HOURS  0 MINUTES WESTERN HEMISPHERE

        :SHOWVAR TZ
        TZ = EST5EDT
        :SHOWTIME
        MON, APR  6, 1998, 10:02 PM

        Now what does this mean?  Specifically, are the clock settings
correct for my system? (The system is located in Ohio, which is in the
Eastern Time Zone of the continental United States). >>


Looks good from here. Since we're now in DST, your UTC offset is -4 hours
instead of -5. Of course, I can't say whether the clock is correct or not.

Steve