Describing the Millennial Kingdom Zechariah 14:16 says, "Everyone remaining from all the nations that came to attack Jerusalem will go up every year to worship the King, YHWH Tzva'ot, and to keep the festival of Sukkot."
Though Purim and Hanukkah are not mandated by YHWH, they are wonderful celebrations of His saving acts for His people. The book of Esther chronicles the original celebration of Purim to commemorate the saving of the Jewish people from annihilation under evil Haman of the Persian Empire. Hanukkah or the Feast of Dedication celebrates the recovery and re-dedication of the Temple, as told in the Book of Maccabees. Maccabees 1--4 were part of the Codex Sinaiticus, the oldest Bible manuscript in existence.
Since the Gregorian calendar and the Hebrew calendar don't mesh perfectly, the festivals fall on different days of the year, according to the Gregorian calendar. Download this printable to keep track of the upcoming holidays! It's free for your personal use!