Sorry, I did not get an notification of the changes of this topic....
Standard in most applications is OK and CLOSE.
OK means "save and close window".
CLOSE means "do not save any changes and close window". This is the same like the cross in the right upper corner.
Normally if you change a value in a window (does not depend on the entry type like calendar, address etc.) a new button should occur: APPLY.
APPLY means "save (and do not close window)".
Therefore APPLY indicates a changed state of the entry, you are just working on.
If you work on an entry and you have to do lots of changes, it is sometimes better to save, when you changed some values. If you loose connection, the changes are saved. Otherwise (at the moment) you can only save your changes by using OK, but that means, that the window is closed as well.
Therefore I suggest to have either two buttons OK and CLOSE, and a dynamically occuring APPLY button, i values were changed, or (if not possible) just the three buttons OK, APPLY, CLOSE.