Pop X to the HH register. This could represent hours or year depeding on whether you are setting the time or the date.
Hours are in 24 hour format and span 0 (midnight) thru 23 (11pm).
Years span 0 (year 2000) thru 99 (year 2099).
It is possible to create an invalid day/ month/ time if you provide incorrect data, though the RTCWriteEvent/Date commands force these to valid values.
RTC documentation and tutorial
Dialect exclusions: Not available in dialects before 16.