I wouldn't worry, in the majority of cases they will have the correct date of receipt on file. It's just that in cases where your application date is, very near to the date there is a change in rules (E.g. Application date of 24 March 2010 & Approval date of 13 April 2010 are very close to the date the rules changed - 6th April 2010) then there could be the potential for CW confusion if they don't have a record of 24/03/2010 as your application date, and thereby may mistakenly apply the incorrect rules.
If you want to check what they have on file, you could make a SAR, but not required IMHO.
Note, they appear to have made a mistake in the number of years granted in the following case... so is always better to be prepared than having to go for correction & reconsideration later on:
http://www.immigrationboards.com/viewtopic.php?t=125577