Eastern Catholic churches observe Sunday (the first day of the week, the Day of Resurrection) as the Lord's Day—the primary day of worship and Eucharistic celebration. Saturday retains significance in the Eastern liturgical tradition as the 'day of the departed' (commemorating the dead) and as a day of liturgical prayer, but Sunday is the central Christian observance and is not the Jewish Sabbath.

A distinctive feature of many Byzantine Rite communities is adherence to the Julian calendar for the calculation of feasts, meaning that Christmas, Theophany, and other fixed feasts fall on dates different from those observed by Western Christians using the Gregorian calendar. Other Eastern Catholic churches have adopted the Revised Julian or Gregorian calendar. The liturgical calendar is extremely rich, with daily commemorations of saints and seasonal fasts.