For special dynamic variables not available in standard, you can build a small periodic report (to be schedule just after midnight every day) that will update some values in TVARV/TVARVC.
Usually there is a standard report RVSETDAT already scheduled, create a customer similar report and schedule both together.
NB: Some other reports can be periodically scheduled related to dates and periods are RMMMPERI, RFPERIOD_OPEN and RKCOOKP1, those reports can be executed before, by or afteryour report to get a full set of coherent variables for your periodic reports. (e.g. generating variable per company for the allowed period for MM movements, or currently opened periods in FI accounting, etc.)
Regards,
Raymond