The Hebrew month is a lunar month, which means that a 12-month year is shorter than the solar year of 365 days. To compensate for that, every so often the Hebrew calendar will include a "leap month" which is an extra month before Passover.
This year included a "leap month" and therefore Easter coincided with Purim, which occurs a month before Passover.
I don't know how the Easter dates are calculated.
I don't know how the Easter dates are calculated.
IINM, it's the first Sunday after the first full moon after the Spring Equinox.
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