Colored easter eggs brightly colored representing the sunlight of spring. The common rule, that Easter Day is the first Sunday after the Full Moon that occurs next after the vernal equinox. It is not an exact rule. The Church constructed tables to be used permanently for calculating the age of the Moon. The vernal equinox is fixed at March 21, not by the actual motion of the Sun.
Easter is always the same in all time zones.
Inevitably, the date of Easter occasionally differs from the date that would be obtained astronomically by the rule. The Julian calendar, which preceded the currently-used Gregorian calendar, is the traditional basis for the ecclesiastical calendar.