Order 2016 Almanac Now - Get 3 FREE Gifts
I couldn't word it anyI couldn't word it any better, so I took it from Wikipedia: Traditionally, the first day of each month is the day (beginning at sunset) of the first sighting of the hilal (crescent moon) shortly after sunset. If the hilal is not observed immediately after the 29th day of a month (either because clouds block its view or because the western sky is still too bright when the moon sets), then the day that begins at that sunset is the 30th. Because of the wildly different locations, the Middle East probably won't be able to see the crescent moon until a day later than the Western hemisphere.

2015 Special Edition Garden GuideCooking Fresh with The Old Farmer's AlmanacThe Almanac Monthly Digital MagazineWhat the heck is a Garden Hod?