The worship of Mithra (or Mithros) started after the first century AD. In fact reading some of the early church writings, they accuse the followers of Mithros of stealing some practices from the Church.
Celebration of Easter is more often known as Pascha in the non English or German world (Passover). Easter is not related to Ishtar, as the germans never really worship Ishtar. It comes from the old Easter services being held at dawn facing east in which the high point was the rise of the sun and celebration of the Resurrection.
I suggest you open up an actual history book.
Here is just one of thousands of exerpts off of web pages when you Google in Easter Ishtar. Have no idea where you are getting your misinformaion from. Cite Sources.
Info below comes from Lew White’s book Fossilized Customs
EASTER EXCERPT FROM THE BOOK FOSSILIZED CUSTOMS — pgs. 12-14
This word has been adopted from Pagans as an attempt to “inculturate” by syncretism a behavior that is absolutely an abomination. If you recognize “Halloween” for what it is, then this will be no different after you learn the truth. Easter was already one of the two biggest celebrations observed by Pagans, long before Christianity came along. It is my belief that when this is exposed, it will fulfill the prophecies of Revelation 18. Go read it now. Babylon is still with us, but it is going to fall. Easter was celebrated by the Assyrians, the Phoenicians, and the Philistines (Goliath no doubt had an Easter basket). You should look up “Easter” in a Webster’s Dictionary, and do further research in other sources! This festival involved the “Rites of Spring” near the Equinox of Venus, when Pagans believed the Earth Mother was impregnated by the sun. They engaged in ritual sex acts, and used symbols of fertility like eggs, rabbits, and “hot cross buns”. The Babylonian symbol for the “female” was, and is, a circle with a crux beneath. The round cakes were baked for the “Queen of Heaven” (Regina Coeli), and “Great Mother” (Magna Mater), with the “cross” symbol indicating the female. The cross also indicated the Equinox, when the Earth’s orbit “crossed” the celestial equator. Hold on now, because everything will be just fine. This must sound so wild you may think I’m a heretic; but by the end of this you will be very glad to have acquired the truth. This book will only shatter myths, not the “rock” of truth.