Job needs to be completed by the entry date. So if you grouted it on the 1st April, enter it in April. It keeps the entries fresh. If you know you've got something better coming up towards the end of April, you can always wait, take photos of both jobs, and see which you feel like entering at the end of April, but don't miss the deadline!
Voting starts 1st of each month and ends on the 21st. Which gives people a week or so to soak in that they have won, answer questions about the job etc, and gives them some time to prepare before starting to vote themselves on the next month etc.
To be honest, with the date thing, I was never too keen on the making sure the date is bang on or else you can't enter situation. The fact is, the system wont let you enter more than one entry per month anyway. So as long as it's one job, each month, and done around the time the JOTM is on, I'm more relaxed than some staff about it.
I haven't stipulated in the terms (so far) to include a photo of a newspaper or your watch or whatever showing the date. I'd like to think we can allow as many people to enter as possible and not risk losing an entry just because somebody couldn't get back to the job with a newspaper to take a photo when it had the bath put in etc etc
So that's up for debate perhaps.