set clock_format <text>
The client uses strftime(3) to create the system clock (%T on your status bar or $Z).
When this variable is unset (the default) the strftime value used to create the clock is either “%R” if set clock_24hour is ON or “%I:%M%p” if it is OFF.
When this variable is set, the client uses this value as the strftime value used to create the clock, and disregards the value of set clock_24hour.
The system clock is updated every set clock_interval seconds when cpu saver mode isn't active. The default interval is 60 seconds, so putting seconds in your clock format won't buy much unless you lower your clock interval.
SET CLOCK_FORMAT first appeared in EPIC4pre1.019.