Although the whole month of Ramadan is very important as thus is the best month to seek forgiveness but it is said that in last 10 days and odd nights try to find lalytulqadar, the night which is better than 1000 nights and angel too come down. mostly 27th of Ramadan is lalytulqadar; the night of forgiveness
The most important date; from my own point of view; is the Hijra (or Immigration date) which is the first day in the Islamic Lunar Calendar. This date marked the start of Islam religion spread. Refer to related question below.
Battle of the boyne, and it is the most cause of trouble date in the calendar as well.
Muslim fasting as the fourth pillar of Islam five pillars is required to be performed during the month of Ramadan (the 9th month in the Islamic Lunar Calendar that is called Hijra calendar year). Refer to question below. Most probably Ramadan will start this year by 10 July 2013.
A time and date calendar can be found on most email portals such as Gmail and Windows Live. One can also access and download a program such as Time And Date.
Its on the American calendar most the time.
The agricultural calendar is most important to agrarian or earth-based religions, where the changing seasons, planting, and harvest cycles are central to their spiritual practices and beliefs. Examples include Paganism, Wicca, and some indigenous religions.
In Islamic countries.
The question as written makes no sense. If you mean "What was the most important Muslim scientific achievement?", see the Related Question below.
The Most Important date after Easter and Christmas is Ascension Day.
Prophet Muhammad (PBUH)
haaj
They are the most important feasts of Mary.
What is your most important accomplishment to date?