How is the date of Easter calculated?

The first new moon after the barely harvest marks the first month of the Jewish year.

On the tenth day the families were to select a lamb. On the fourteenth day (the day before pass over) it was to be slaughtered at twilight as the Passover lamb.

By the time of Jesus the Jews had "standardize" the calendar and it was no longer dependent on the ripening of the barley crop.

By working backwards and using the Jewish calendar it is possible to determine the date. This comes up with a window about three years long. The three year window is in mostly caused because of an argument over exactly which day of the week was the crucifixion. If Jesus was crucified on Friday then the three nights in the tomb are not possible. To get the three nights requires Jesus to be crucified on Thursday. This goes against tradition but is more then likely correct. Friday would have been the actual Passover Sabbath, followed by the weekly Sabbath. This use of the Jews to call every religious holiday a Sabbath has caused a lot of misunderstandings over what day is what.

So yes it is possible, but because of a conflict between tradition and what the Bible actually says some debate is possible.

Easter is the Sunday following the first full moon after the vernal equinox.