Bottom line:
COTM 02 entries will be permitted until approximately* 13:00 UTC on 1st August.
GOTM 33 entries will be permitted until approximately* 13:00 UTC on 16th August.
Wherever you live these times should be past your midnight on the closing dates. If you live in New Zealand you'll get most of the next day as well.
Here's the full story:
Ainwood defines the Start and Finish dates for each game. He puts them into the games database, and separately sets up the game page. The game page doesn't currently read them from the games database. The submissions page does.
In the database COTM 2 is set to Finish on July 31, and GOTM 33 is set to Finish on August 15. If the COTM 2 page says July 30 it's wrong
The submissions page operates off these database dates, and compares them with the database server's clock. The server is currently running about 8 minutes fast relative to UTC - 7 hours. When Daylight Saving ends the hours offset will become UTC - 8 hours as the server clock will drop back one hour.
The submissions page starts to accept entries for each game as the server's date clicks over to the Start Date (or later if Ainwood puts the game into the database after release).
The submissions page accepts entries for each game up to 4 hours after the server date clicks past the Finish date. This time represents mid day UTC on the day after the Finish date, ignoring Daylight Saving. And that's midnight on the Finish date at the International Date Line - the last place on earth where the Finish date ends.
Now I bet you wish you'd never asked
* NOTE: The minutes offset varies as the server doesn't seem to be synchronised to anything in particular, so you should not rely on using the last 30 minutes of the deadline. 
