Does the mayor of NYC actually have authority over the schools or is he just flapping his mouth?
Difficult to schedule in advance like Jewish and Christian holdidays. Muslim holidays [ see here ] of Eid al-Fitr, Eid al-Adha cannot accurately be scheduled according to the Gregorian calendar used in US. Actual date won't be known until the new moon is sighted and then Muslims do not agree on dates.
DeBlasio missed that part of the scenario!