As salaamu alaikum wa rahmatullahi wa barakaatuh,
Here is a benefit that Sheikh Uthaimeen brought when asked about The Night of Decree that we wanted to share with you all:
Does the night of Decree change from year to year or is it a set date?
First of all it is necessary to say that the scholars differ in this matter.
But the correct opinion is that it moves around from year to year. One year it is on the 21st, the next on the 29th, the next on the 25th and so forth. We say this because there is no way for us to join together all of the different narrations.
The reason for the fact that this blessed nights moving around is that if it was one specific night then the lazy people from among us would not work hard except for that one particular night. But being as though is changes from year to year the chance of it taking place at anytime causes the people to work very hard all ten nights.
[This can be found in his book Sharul Mumte’a in the book of Siyaam]