Abrahamic / Middle Eastern Islam How to Use the Moon to Figure out When Ramadan Begins Share Flipboard Email Print da-kuk / Getty Images Islam Ramadan and Eid Al Fitr Important Principles Prayer Salat Prophets of Islam The Quran Hajj and Eid Al Adha By Huda Islam Expert M.Ed., Loyola University–Maryland B.S., Child Development, Oregon State University Huda is an educator, school administrator, and author who has more than two decades of experience researching and writing about Islam online. our editorial process Huda Updated June 25, 2019 The Islamic calendar is lunar-based, with each month coinciding with the phases of the moon and lasting either 29 or 30 days. Traditionally, one marks the beginning of an Islamic month by looking at the night sky and visibly sighting the slight crescent moon (hilal) that marks the beginning of the next month. This is the method which is mentioned in the Quran and was followed by the Prophet Muhammad. When it comes to Ramadan, Muslims like to be able to plan ahead, though. Waiting until the evening before in order to determine if the next day is the start of Ramadan (or Eid Al-Fitr), requires one to wait up until the last minute. In certain weather or locations, it may even be impossible to visibly sight the crescent moon, forcing people to rely on other methods. There are several possible problems with using the moon to signify the beginning of Ramadan: What if people in one area sight the moon, but those in another area don't? Is it okay for them to start and end the fast on different days?Should we follow the moon-sighting in Saudi Arabia (or any other area of the world), or should we sight it ourselves in our local community?What if our location is overcast and cloudy and the moon is not visible to us?Why do we even bother looking for the moon, when we can astronomically calculate when the new moon is born, and thus when the crescent should be visible? That eliminates human error, right? Although these questions come up for every Islamic month, the debate takes on more urgency and significance when it comes time to calculate the beginning and end of the month of Ramadan. Sometimes people have conflicting opinions about it within a single community or even a single family. Over the years, various scholars and communities have answered this question in different ways, each with support for their position. The debate is not resolved, as each of two strongly held opinions have supporters: The first prevailing opinion is that one should commit to a local moon-sighting, i.e. begin and end Ramadan based on the sighting of the moon in your local vicinity. Astronomical calculations can help us predict when the moon *should* be visible, but many Muslims still prefer to follow the traditional method of looking at the sky themselves to physically "sight" the moon.Another prevailing opinion is that with the technology we have at our disposal, one should calculate when the new moon is going to be born, and base the calendar on that. The advantage is that lunar phases can be measured quite precisely, making it easier to plan ahead and ensuring no mistakes. Preferences for one method over the other are largely a matter of how you view tradition. Those devoted to traditional practice are likely to prefer the words of the Qur'an and more than a thousand years of tradition, while those of a more modern attitude are likely to base their choice on scientific calculation.