how can I see when someone was last online

I don't think you can.. I'm not sure if it comes up when you do a search but have my doubts.
Someone smarter than me maybe able to help you.

I just did a search by clicking the Search button on the top of the main page.. when it comes up there is a button along the top to see who is actually online but not when someone was last online

Let's see if I can help you on this. Go to the member's profile (whom you want to know was last online) and look at the top of the profile where it gives his age, gender, and what he is looking for here. The last sentence will roughly tell you when that member was (or is) online.
I just went to ur profile and it said "Online now!". As soon as you go offline it will say,
"Last seen within the last day". If you've not been online here for more than a day, it will say, "Last seen within the last four days". If more than four days have elapsed, it will say, "Last seen within the last week". Down the line it will say, "Last seen within the last two weeks"; "Last seen within the last month"; or "Last seen more than a month ago". This last statement could mean just that (more than a month ago) or it could mean even five years ago! I guess the algorithm for this part of the program/software counts only up to one month!

And if it comes up offline could that mean thay havnt bien on for a very long time

And if it comes up offline could that mean thay havnt bien on for a very long time