It's three weeks (21 days) give or take a day or so. But watch out! Because it's the MIDDLE WEEK when they can so easily get pregnant. Then they will try anything to get to a male dog, they will jump fences....wriggle underneath things to get out, etc. And once they are mated and they "tie together" it's too late! Preggers doggy! And that can happen in just a minute or two. Dogs don't mess about! lol.