How Many Weeks In A Calendar Quarter. Week number from date to date; 3 quarter to week = 39.10714 week. Supersized quarters Some companies report quarterly info from www.cnbc.com 26 weeks is 6 months (â½ That adds up to 52 weeks (where each week is exactly 7 days) plus 1 or 2 additional days. Week number from date … Continue reading How Many Weeks In A Calendar Quarter