InterSystems FAQ rubric
$ZTIMESTAMP returns the date and time in UTC format, so to change it to the local time zone, use the following system method:
$SYSTEM.Util.UTCtoLocalWithZTIMEZONE($ZTIMESTAMP)
The above output will be in the format ddddd,sssss.fff.
ddddd: Same format as $HOROLOG dates
sssss: An integer indicating the number of seconds elapsed since midnight on the current date
fff: Variable number of digits indicating the fractional part of a second
* Similar to $HOROLOG, except that $HOROLOG does not include fractional seconds.