For Muslims here and around the world, Eid al-Fitr marks the end of the holy month of Ramadan with a day of prayer followed by celebrations.
But in a quirk of the lunar calendar that determines the start of Eid, the holiday this year will occur around Sept. 11, when many Americans will mark with somber remembrance the terrorist attacks that killed more than 3,000 people nine years ago.
This year, prayer services will still be held on the first day of Eid, which is expected to be Friday or Saturday. But to avoid celebrating at a time other Americans are mourning the tragic events, many Muslim families and mosques are delaying Eid celebrations by a day or even a week.
"It's out of respect," said Kabir Jeddy, treasurer of the Muslim Association of the Puget Sound, MAPS, a Redmond mosque. "It's not that we are putting our lives on hold altogether, but it's not a day we want to be out celebrating."
The already sensitive timing of Eid and the 9/11 anniversary has been made even more so by a confluence of developments that in recent weeks and months have put Islam in the spotlight.
A proposed community center and mosque near where the Twin Towers stood before the attacks in Lower Manhattan has divided Americans, with two-thirds of those surveyed in a recent Washington Post-ABC News poll objecting to the proposed complex.
A protest over its siting is scheduled for Sept. 11 in New York on the same day a Florida pastor has threatened to burn copies of the Quran, sparking international condemnation.
Ramadan commemorates the seventh-century revelation of the Quran to the Prophet Muhammad and Muslims mark it in part by fasting each day between dawn and sunset.
The timing of Ramadan is determined by moon sightings - with the month beginning with one new moon and ending with the next.
Ordinarily, families and Muslim groups then host Eid parties or mosques organize larger family-style celebrations.