if you click on their name there is a spot that says "last login" or "last logon". That should help.
time when opponent was last online

Yes, when you visit someone's main profile page you should see something to the effect of " Last Login: Jan 23, 2009 " as an example. This will not show you the exact time of the last login, but rather the date when they were last logged into the website.

View Players (click on MY HOME, then Online Chess, then View Players) will show you how long since someone was last online; in hours - if less than a day; in minutes - if less than an hour.

Got it artfizz, it's just that you wrote: "View Players (click on MY HOME, then Online Chess, then View Players)"
So I clicked on My Home and could not find the link.
I am not sure which is it you did, a lapsus calami, an erratum, a mendum or a parapraxis?
There is no word in the latin language for a keyboard mistake, don't really know why!
Thanks for the tip.
ellipsis.
is it possible to find out when an opponent was on the site last?