Does the meridian time or the meridian time written in the calendar affect the validity of the prescribed prayer times found therein?

The fact that the calendar is based on the astronomical (Zawaali) time does not affect it, as long as it is approved by the legitimate religious authorities and specifies the prayer times. The daily calendar is divided into غروبي (sunset-based) and زوالي (astronomical noon-based), and the Zawaali is the common one today.