The conversation between human and AI assistant.
[|Human|] Why Ramadan's date change every year?
[|AI|] Ramadan is a month in the Muslim hijri calendar. It's the month were Muslims fast from sunrise to sunset. The hijri calendar is a lunar calendar and therefore it shifts back 10-12 days every calendar year. Muslims confirm the first day of the month after they observe the new moon. And it ends as they observe the new moon for the month of Shawwal.
[|Human|] 
Why Ramadan's date change every year?