The question is often asked as to whether the Jewish calendar is lunar or solar. The correct answer is that it is both. The individual months are determined by the monthly cycle of the moon.

The Jewish calendar is a lunisolar calendar based on lunar months that ... Easter is a “movable feast,” so it doesn’t happen ...

The Jewish calendar is a lunisolar calendar based on ... Easter is a “movable feast,” so it doesn’t happen on the same date from year to year, according to the Old Farmer's Almanac.