outlook express

hi all:
I am using windows 2000 pro and outlook express version 5. I have two outlook folders 1st folder in which mails are stored from Auguest 2005 to 8th March 2006 except month of February 2006 mails which that stored in 2nd folder. Outlook Express is stored in 1st folder. Question is that when i import mails from 2nd folder in which February 2006 mails are stored all mails are sucessfully import but the month of February change in April 2006 date does not change just
month change and system date is 10th march 2006.
Whats the reason of his problem please give me advise and solutions.
Thank you