should the entries be submitted by 07:30 UTC Monday 21 August
I'll be honest I don't know any other way to say what I'm saying with the following line. I had thought it was totally, crystal clear.
ENTRIES MUST BE SUBMITTED BY 07:30 UTC Monday 21 August
I'll say it again though...
Entries...
must...
be...
submitted...
by (this is the operative word here)
07:30 UTC...
Monday...
21 August.
Hopefully that makes it clearer. If you can't get it from that, well, I'm afraid you're in some trouble moving forward in life.