Experimental Physics and
Industrial Control System

There's certainly a way to do this with base, but on an APS beamline, I would do it like this:

devIocStats maintains a time-of-day string PV, here called xxx:TOD, which updates every second.  When the _expression_ xxx:TOD=="00:00:00" changes value, the string calc writes that value to the calcout record's B field, and causes it to process.  This sets the calcout record's VAL field to -1 when TOD=="00:00:00", and then to 0 when TOD=="00:00:01".  Otherwise, the calcout record's VAL field increments whenever it's processed.