
Hi,
Bitches are normally in season for about 3 weeks each (about) 7 months. No hard and fast rule, each season in each bitch is different!
The fertile period in each season lasts about 5 days, and averages at round about day 13 of the season. Although bitches have been successfully mated as early as day 3 and as late as day 22. One of my bitches was at her "best" on day 17.
Hope this helps :)