The purely lunar year of the Islamic Hijri calendar can have 354 or 355 days, (i.e., in a 30-year cycle, 11 years have 355 days and the rest 354 days). Accordingly, the lunar year is shorter than the Christian Gregorian solar year from 10 to 11 days. Consequently the Islamic events and festivals gracefully pass through all four seasons.

It is interesting to note that the birthday of the Holy prophet (12th Rabi-ul-Awwal) occurs generally 71 days after the commencement of the Hijri year (1st of Muharram). The first of Ramadan occurs one hundred and sixty-six days after the holy Prophet's birthday. Ramadan as well as other months sometimes have 29 days and sometimes 30 days. Then the Eid-al-Adha (10 Dhul-Hijjah) generally falls 98 days after the 1st of Ramadan.

There may be the variance of one day between the dates given in this Schedule and the actual sighting (NOT the invisible birth of the astronomical New Moon) of the Crescent in a particular horizon, which alone determines the feasts, festivals and Eids for the people of the locality. Muslims should also realize that a Crescent following a month of 30 days, will look larger and stay longer than the Crescent following a month of 29 days.