There are calendars apart from the one we see in our daily life which is Gregorian. The one where February has 29 days every four years otherwise it is stuck with 28 only.
Among those calendars, there is one called the Hijri Calendar or for non-Muslims it is known as the Islamic Calendar. Like the normal calendar, it have the name number of months. The one thing that is not same are the days and their surety. There are either 30 or 29 days of each month. Technically, it is the same as Lunar Calendar. Whenever the crescent appears, it marks as the beginning of another month.
Being unsure brings the mystery of when we are having those days off for Eid (Islamic Event).
Eid occurs twice a year within 2 months and 10 days apart. The first Eid – Eid Al Fitr (عيد الفطر) – happens right on the first day right after the month of Ramadan ( رمضان ). The second Eid – Eid Al Adha (عيد الأضحى) – is celebrated on the 10th day of Dhul Hajj ( ذو الحجة ) with a sacrifice of a sheep, goat, cow or camel (if one can afford).
This year, 2019 (1440 Hijri) Eid Al Fitr is occurring on either Wednesday, 5th of June or Thursday, 6th of June. Having uncertainty the public holidays started on Tuesday, 4th of June for the pupil to clear their mind and get ready.