It was a perfectly understandable question. Perhaps we could just let members of each of the Eastern Churches represented here answer. If he gets numerous different answers from different churches, isn’t the same purpose of educating him fulfilled, without making the poster feel inadequate and inferior?
In the Byzantine Rite, we celebrate Vespers combined with the Divine Liturgy of St. Basil the Great on Christmas Eve. Great Compline is celebrated late in the evening, as well as Matins at some point. The Christmas Day Liturgy is the Divine Liturgy of St. John Chrystostom. The timing of the services can vary greatly, depending upon local needs. My parish will celebrate Vespers/St. Basil the Great in the afternoon. Great Compline will be in the evening, perhaps followed by Matins. We likely won’t do Matins, though. The liturgy of St. John Chrystostom will be celebrated on Christmas morning, around 10:00 am. We’re still waiting on our priest to firm up the schedule.
Christmas Eve is a day of strict fast, during which traditionally no food is eaten until the first star can be seen. We have the tradition of a Holy Supper, which is observed by many Eastern Europeans, east and west.
en.wikipedia.org/wiki/Holy_Supper.