To improve the digital connection among Islamic and Christianity heritage in the Balkan region, we have developed several procedures for reconstruction oldest calendric rules of both confessions. Also, one part of the paper refers to the islamic prayer schedule calculation. This possibility is produced from an original algorithm for high accuracy Sun and Moon's ephemeris calculation - in the case of calendars it is a calculation of the so called cycles of the Sun and of the Moon. Regarding to civil rules and religious rules of Christianity and Islam we have generated calendars over real time intervals. The conditions for proleptic calculation are done, too. The algorithms for mutual conversion of these calendar systems and their social events are connected via Julian day number.