Allah, Exalted is He, decreed that the sighting of the new moon (crescent) should be usedto determine the timing of the lunar months. The sighting of the crescent marks the end of one lunar month and the beginning of another. Based on that sighting, many religious obligations are determined such as fasting and Hajj. In this hadeeth, the Prophet ﷺ commanded us to fast Ramadan upon sighting the new moon after sunset on the twenty-ninth day of Sha’baan, and break the fast when the crescent moon is sighted after sunset on the twenty-ninth day of Ramadan. This means that the lunar month may be twenty-nine or thirty days, and both scenarios are possible and valid. However, determining the times of fasting and breaking the fast depends on the sighting of the new moon. If the crescent moon of Ramadan is not sighted for any given reason, such as clouds and the like, we are commanded to complete thirty days of Sha’baan; likewise, if the crescent moon of Shawwaal is not sighted, we should complete thirty days of fasting in Ramadan..