City public schools will regularly close for Islam's two holiest days -- the first religious additions to the academic calendar since the Jewish High Holy Days in 1960.

Closure dates for Eid ul-Fitr and Eid ul-Adha, announced Wednesday by Mayor Bill de Blasio, will vary year to year because Islam follows a lunar calendar. The new school holidays are set to begin in the 2015-2016 school year.

"A holiday of supreme importance to the Muslim community will be recognized in our school calendar, so that children can honor the holiday without missing school, so that families can be together on the holiday, so that our city respects and embraces this important and growing community," de Blasio said.

The city must adjust the calendar annually to fulfill the state-mandated minimum 180-day school year. About one-tenth of students are Muslim, according to a 2008 Columbia University study.

Eid-ul-Fitr marks the end of the holy month of Ramadan, and Eid-ul-Adha commemorates the completion of the pilgrimage to Mecca that Muslims are encouraged to make.

In the next school year, Eid ul-Adha will be marked on Sept. 24. Although the observance date varies among Muslims, the date was picked based on a consensus among city Muslim leaders.

Eid-ul-Fitr in 2016 will be about July 5 -- a Sunday after the regular school year.

City Muslims have long sought to add their holidays to the Christian and Jewish observances that public schools recognize. In 2009, the City Council passed a nonbinding resolution urging the Eid holidays' inclusion. But then-Mayor Michael Bloomberg said no.

"If you close the schools for every single holiday, there won't be any school," Bloomberg said then. De Blasio promised in his campaign to reverse that decision.

The Eid inclusion is the first additional day off added to the school calendar since 1991, when Presidents Week became an official school recess. The last additional holiday was Martin Luther King Jr. Day, in 1978. Closure for Yom Kippur and Rosh Hashanah started with the 1960-1961 school year, according to the city's Department of Education.

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De Blasio announced the new school holidays at a rally at PS/IS 30 in Brooklyn's Bay Ridge before Muslim New Yorkers in kufi head caps, ankle-length thobes, hijab headscarves, and abaya tunics.

"We can now say that we are multicultural, multiracial, multi, multi, multi-everything city," de Blasio said.

In 1960, when the city school system adopted Rosh Hashanah and Yom Kippur closures, the city's top educator at the time discounted any religious motivation behind the closure, citing only "administrative reasons": chronic absenteeism by teachers and students.

When the Muslim holidays have fallen on a school day, more than half of teachers and nearly three-quarters of students don't show up at PS/IS 30.