re-entering Canada

[curiosa]

Hello to everyone..........and thank you for your help in advance.

My boyfriend just visited me and we had a short 2-week vacation together in Canada (I am a Canadian citizen).  When he arrived, Immigration wrote the date Feb 5, 2011 on his passport, meaning he was allowed to stay until then (I imagine).  He has since returned home, but I was wondering if he's allowed to come back into Canada (having this date on his passport), and if so, how long he has to wait before he can re-enter the country.  Thanks and best wishes to all of you!