In the Christian tradition it is a holiday commemorating the birth of the Jesus of the Christ. This liturgical holiday is permanent, falling on 25 December (according to the Gregorian calendar). God giving birth is preceded by the period of four-week expectation (of precisely four Sundays), called Advent. At Churches which still are celebrating liturgy according to the Julian calendar (so-called Eastern Churches, mainly Orthodox church), God giving birth is falling at present to 7 January.
The Easter is an oldest and most important Christian holiday. The Easter is a movable feast. Perhaps to fall out on 22 March and 25 April. Enough long they were disputing when the Easter was supposed to be get around. Only during the Nice council in 325 r.. it was settled that she will care about us on first Sunday after the spring full moon.