"Dahwul Ardh" - the 25th of Dhul qa'dah, according to a tradition of the Holy Prophet (P.B.U.H.H.) reported by one of his Sahabi - 'Abdullah bin Mas'ud, is the day when the earth was spread for the advantage of human beings. The phrase "Dahwul Ardh" literally means "The spread of the earth". In another tradition it is reported that the first Rahmah & blessing descended on this very day.
Hence it is a very important occasion indeed. According to a tradition of the Holy Prophet (P.B.U.H.H.), whosoever fasts on this day his fast would equal 70 years of fasting.
Having known these merits, should we limit our celebration with fasting and the expression of joy, or should our struggle transcend beyond that? This obviously would depend on our vision about this important day. And in order to understand properly the importance of this day, we should understand the earth better.
source : http://english.almaaref.org