There are three sources of the Jewish holidays.
The Torah commands the observance of five annual holidays: Rosh HaShanah, Yom Kippur, Sukkot, Pesach (Passover), and Shavuot. These are the most sacred of the Jewish holidays.
Many others come from Jewish tradition, such as Chanukah and Purim which commemorate significant events in the history of the Jews.
Four holidays were established by the Rabbinate of the State of Israel.
The observance of all of these holidays is according to the Hebrew calendar. The nature of this lunar calendar can cause the dates to vary by as much as one month on the Gregorian calendar. The holiday dates for the next few years can be found on the URJ Calendar of Jewish Holidays.