Reference date in tool_sectodat and tooldatetosec

Hello crocoers,
I want to use the option #define USE_CALENDAR, then the function tool_sectodat and tooldatetosec are used in the model. In the source code of tool_sectodat and tooldatetosec function, the tref = 59958230400_rlg, so I assume that the reference date is 19000101 00:00:00, is it right? I recommend to explain clearly that the reference date is 19000101 00:00:00 in the code of the two functions.

Best
Changshui