The method for determining the date of Easter is complex and has been a matter of controversy. Put as simply as possible, the Western churches (Catholic and Protestant) celebrate Easter on the first Sunday following the first full moon after the spring equinox.
But it is actually a bit more complicated than this. The spring (vernal) equinox is fixed for this purpose as March 21 (some years it falls on March 20) and the "full moon" is actually the paschal moon, which is based on 84-year "paschal cycles" established in the sixth century, and rarely corresponds to the astronomical full moon. These complex calculations yield an Easter date of anywhere between March 22 and April 25.
The Eastern churches (Greek, Russian, and other forms of Orthodoxy) use the same calculation, but based on the Julian calendar (on which March 21 is April 3) and a 19-year paschal cycle.
Thus the Orthodox Easter sometimes falls on the same day as the western Easter (it does in 2010 and 2011), in other years the two celebrations can occur as much as five weeks apart.
In the 20th century, discussions began as to a possible worldwide agreement on a consistent date for the celebration of the central event of Christianity. No resolution has yet been reached.
Many gypsies are devoutly Orthodox Catholic and do not follow the wiccan/pagan traditions or wheel of the year. Many pagan or wiccan practitioners celebrate Easter as well as Ostara as the two are not mutually exclusive.
In fact, over the centuries, the religious observances of Easter have been supplemented by popular customs, many of which were incorporated from springtime fertility celebrations of European and Middle Eastern pagan religion. Rabbits and eggs, for example, are widely-used pagan symbols for fertility. A common custom is to hide brightly colored eggs for children to find.
Source: Religion Facts