Just a quick(ish) couple of questions.

Does the api index.php file work by informing WordPress that an update is necessary if the date OR the version are different (or both different)? And does it make a difference what the actual date is of the new version (zip file), i.e. is it just the date specified in the index.php api page that rules whether an update is necessary.

Also, if I wanted to update just by version number and date, is this easy to do?