How accurate is the RTC function blocks in Zenon Logic ?

How accurate is the RTC function blocks in Zenon Logic ?

Greetings all,

Does the RTC built-in function blocks in Zenon Logic reliable to use in a time critical application ?

I'm trying to calculate the amount of energy consumed by a device using a custom soft totalizer I wrote in Logic. If I used the RTC functions to govern the process, will the reading be accurate on the long run ? i.e. incorrect drifting of values with time.

I'm dealing with a resolution of 1 second meaning that precisely every 1 second I need the code to be executed, not before and not after.

Regards.