A thin lunar crescent which can be noticed by naked eye after conjunction called "hilal" is a past of moon phase which is used to judge the beginning of the new month in Hijriah calendar.Moon phase is actually a reflection of the combination position of the earth, the moon and the sun.the complexity of hilal's visibility may not enough to predict or to descript the halal's visibility by simple criteria for all hilal.the appearance of two similar moon phases will be occurred every 235 lunation or about 19 years, it is know a Metonic cycle.We use 235 lunation as basis for grouping the data for the purpose a study on determining the beginning of new month in lslamic lunar calender.