Millions of Muslims across the world are celebrating the first day of the Eid al-Fitr holiday, which marks the end of the monthlong fast of Ramadan.

Families dressed in their finest clothes and children carried their new toys as they headed to mosques early Monday morning to observe traditional Eid prayers.

But the mood was dark for millions of people affected by the Syrian civil war, the Gaza war and the militant advance in Iraq.

Muslims in Indonesia, Malaysia, the Philippines, across the Middle East, Europe and the U.S. are celebrating Eid Monday. Millions in India, Pakistan and Morocco are still fasting and will likely celebrate Eid on Tuesday.

Muslims use a lunar calendar and a moon-sighting methodology that can lead to the month of fasting ending on different days.