Simplify the following text for a Grade 10 native English-speaking person.
Original: Hanukkah is observed for eight nights and days , starting on the 25th day of Kislev according to the Hebrew calendar , which may occur at any time from late November to late December in the Gregorian calendar .
Simplified: Hanukkah is observed for eight nights , starting on the 25th day of Kislev according to the Hebrew calendar , and may occur from late November to late December .