
As i humans you count from first day to first day.
My own bitches have gone anything from 4 months from last season to over 9 months. It often takes a year or two for a regular pattern to emerge in some individuals, and others are never predictable,a and some you could set your clock by.
Anything between 4 and 10 months would be usual.
I have found that while in season bitches seem to have less bladder control, as regards holding as long as normal, and I have found peeing on beds with girls that have just Had pups, so may be a hormonal marking issue.