The 1st passover was in Egypt.
The first day of Passover in 1836 was April 2nd.
All over the world.
Passover occurred in April 2016 from April 22nd to April 30th.
Passover in 2013 was from March 26th to April 1st or 2nd, depending on what country you were in.
Officially it was the year after they left Egypt, but it wasn't celebrated.
Yes, they absolutely can. Since passover is seven days (or eight in the diaspora) it must occur at least once.
In 2010, Easter Sunday was the 6th day of Passover. Those often seem to occur close to one another. Wonder why that is.
Shevuos is about six weeks after Passover. If Lag BaOmer counts, then about two weeks after Passover is Lag BaOmer.
49 The seventh Sunday after Easter, commemorating the descent of the Holy Spirit upon the disciples.
The religious ceremony held on the first two nights of Passover outside of Israel (1st night only in Israel) is called a Seder. The word Seder means 'order'.
Ishtar is a pagan fertility goddess whose rites occur in Spring, close to Passover. While the "holidays" were combined by the Catholic church, many sects do not recognize the blending of Ishtar worship with Passover.