Quickly though: Islam follows a lunar calendar that is not fixed by season. Islamic holidays "float" 10 days each year on the Gregorian calendar. We also only have 352 days in our lunar calendar, compared to 365 1/4 in the Gregorian calendar. Eid ul Fitr marks the end Ramadan, and Eid ul Adha marks the end of the pilgrimage to Mecca. Below I explain things a bit further.
Firstly: There are two Eids, both are three days long. In the West, or rather in particular in the United States where work and productivity lead to people leaving home to go to work or school at obscenely early hours before the sun rises, religious holidays and traditions are abbreviated. The word Eid means "festival", and as festivals are usually longer than 24 hours, so are the two Eids. The first day of Eid is usually spent in prayer, attending special high services in the morning, and conducting acts of charity, piety and sacrifice, followed by visiting immediate family in the evening. The second two days involve visiting friends and extended family, and more acts of charity. Legally, across the Muslim world, business and school has generally-speaking stopped for three whole days. However, in America most Muslims (unless they're brave enough to risk losing their job or falling behind at school) take off only the first day of Eid. (Sidenote commentary: our culture is way to work-focused and in the long run that short-term view of achieving immediate productivity will do us more harm than good.) In other words: Like Passover, Eid is a multi-day event and if it is denoted on a calendar, it should be denoted as such, not as a single day--that's misleading and religiously speaking, plain wrong.
Secondly: Muslims do not agree on when Eid is. I suggest people read this well done piece by NPR on the matter. I assure you: Muslims have never and will likely never have a uniform date accepted across cultures, sects, and legal schools of thought on when Eid ul Adha and Eid ul Fitr occur. Legally speaking, Sunni Muslims have traditionally empowered local communities themselves to seek out the correct phase of the moon to establish the lunar date for an upcoming holiday. Really: for me to know when Ramadan, the New Year, or when either of the Eids begin, Emmalee and I go outside, wait for sunset and search for the new moon (and in the case of Eid ul Adha, we count ten nights following the new moon). Sunnis are roughly 75-80% of all Muslims worldwide, while in Montgomery County they're roughly 55-60% of all Muslims. Emm and I are Sunnis.
Shiites generally follow a different calculation, and while there has been an effort to use an astronomic date in both sects, the last few years the projected astronomic date has been blatantly wrong to the point that entire congregations and their Imams in Montgomery County began fasting for Ramadan or celebrating either Eid on a wholly different date than what the astronomic projected date (favored by the Eid Coalition) was. That can be confusing, and incredibly difficult for people trying to give a school or work day off to Muslim students and workers.
In particular, the majority of congregation and the Imam at the Islamic Center of Maryland in Gaithersburg, along with the board, Imam and congregation of the Islamic Society of Germantown began fasting for Ramadan and celebrating Eid ul Fitr (the end of Ramadan) on a date different than what was predicted astronomically (again, the method being used by the Eid Equality Coalition). Those two congregations together represent more than 1/3 of the counties Muslims, and represent the younger, growing sections of the community versus the older, shrinking sections down and east county. Again: Shiites dates did differ, and another 1/3 of the Montgomery County's Muslims waited to know when Saudi Arabia, where Islam's holiest shrines are, would celebrate the Eids and Ramadan this year.
Why Can't Y'all Just Agree On A Date?
To explain why so many Muslims still seek out a visual sighting of a new moon to denote the beginning of a Muslim holiday, new year, or month: there is an Islamic saying often attributed to Islam's prophet Muhammad (peace be upon him): God finds marketplaces the least desirable place for Humanity, and that mosques (i.e. places of worship) are the places most loved by God. What does the saying really mean? Focus less on the material world and its life around you, let go and focus on loving God. As a result of this focus on spirituality, Islam has legally emphasized the seeking of the date of religious holidays by individuals and local communities themselves as a way of forming a bond with God.
So Where Does This Leave MCPS?
Well, first of all let me state that I have known some of the Board of Education members a really long time. I don't think any of them harbor ilk or distrust towards their Muslim constituents or the countless Muslim students in their care. If anything, they all likely know that Muslims do not, and cannot agree on a single starting point for Eid. They also have been briefed by me, a law professor at Howard University, and several Imams and community leaders that Eid is three days long, not a single day, and if they are going to put Eid on any calendar, it should be three days (as a practical note, more than likely the first day of Eid for any group of Muslims would likely fall into any of the three days following the astronomically predicted one). The school system cannot legally give a school day off for one religious group or another due to the rise of judicial activism on federal court benches, and the (good) generally-held principle that state and religion are constitutionally separated, always. Instead, if a religious holiday incurs monumentally more absences than not, then schools will close. The average absentee rate for MCPS has held steady at 5.0%. On the date suggested by the Eid Equality Coalition as Eid in a past year, absentees were 5.8%. Not much higher, and given that the county has 15 active Muslim Student Associations in its high schools alone, it could have been much, much higher. Again: this points to Muslims not agreeing on the dates of our high holidays (and we really would prefer the county not to choose a date for us).
Where this leaves us is the following: in the past decade, it is believed by the Eid Equality Coalition (and myself) that over 100,000 Muslims now call Montgomery County home. That's one-tenth of our county. While the Eid Equality Coalition has done an incredible job in raising awareness about the two Eids, most of our Muslim community is frankly, brand-new to the county, and we are still building our community's organizational capacities (just this year alone, three new mosques opened, and generally a mosque brings with it a congregation of 3 to 5 thousand worshippers on high holidays). We're working feverishly to build our community's organized presence in the county, and until that happens we won't have a clear idea of what most Muslims expect the school system to do about Eid. What I will say is, that when teachers in the past have blatantly ignored the county's policy of not assigning homework, conducting new instruction or having quizzes or tests on or around religious holidays, it has fed a narrative of institutional bias against Muslim students. I and others have pled and made absolutely clear to our Board of Education that this remains a problem to be dealt with effectively and immediately.
However, I applaud the Eid Equality Coalition's efforts. While as I have made a case above for disagrees with their declaration of what, how and when Eid is celebrated by Muslims, the coalition did do the heavy-lifting of organizing a tremendous effort to recognize the unique challenges faced by Muslim students in our county school system.
More articles about the rather unique ways Muslims calculate their holidays are below: