What it the RTC_TYPE?
I can find no documentation on this in the Help file. I understand that it represents a real time clock, but it appears that nothing can be done with this type. Math is not allowed(which I would like to do), and converting to TIME isn't allowed.
Comments
It is used by the RTC global variable to store the system time.
You can declare other variables using this type, but this will only create a STRUCT variable containing the fields defined by that data type (HOURS, MINUTES, SECONDS, etc).
You can use the individual fields of the RTC variable as inputs to arithmetic operations, and then store the results in other variables e.g. in the fields of another variable of type RTC_TYPE.
Apart from the String variable that is returned from the RTC_S function, there isn't any other format of the current time available directly in IEC code from standard PLCnext Engineer functions, that I'm aware of.
https://www.plcnextstore.com/permalinks/apps/latest/60002172000027