Calendar lost after software update!

My husband recently updated the software on my iPhone 4S.

In the process, I seem to have lost all my calendar entries (appts, meetings the works!), that were linked to my Outlook (aka Hotmail) account.

BTW - I never realised they were linked and didnt need them to be in the first place.

However.... the only entries that are there are 3 that were repeat entries for each week/fortnight etc and one is even outdated by about 5 months.

I have about a gazillion appts coming up that I now cant find.

Any help appreciated.