Why muslims celebrate festivals by looking at moon?

r u bull*******g???prophet copied it from bible???r u nuts???.....the qoran ws revealed to him.......the quran is the same from then on...its not changed like the testaments!!.....we(muslims)dont worship the moon but follow the lunar calender.......earlier ppl used to follow this to know the dates and months!!....we believe in sighting the moon rather than knowing it from a meteorological umptions!!......