Can you guarantee a short calving season?

I used a bull on my early bred cows last fall, the one I used for AI. So I wanted to find out whether I can get all my births relatively close together so I can do 60-day calving seasons if I wanted to. I have 13 cows bred to this bull. I did confirm whether they were bred to him or a cleanup bull. I have info on the estrous cycle for all the cows I bred to him so I can calculate the gestation length for all the cows that were bred to him. I know there are anomalies whether it’s an error in record-keeping, a cow coming into heat early or late with a shorter or longer cycle, or a real anomaly in gestation length. Since I’m lazy I didn’t put all the data points in, but the median and mode is 283 days. That’s within the normal range for gestation length. If I use the 283 day length, and I know the date a cow had a verified heat cycle, I can calculate the breed date of the next heat cycle. If I’m missing some data, I can use the breed date to calculate the next heat cycle after breeding. So I get the range of dates I bred the cows to this bull. The shortest range of dates I bred the cows to the bull is 27 days. The longest range of dates I bred the cows to the bull is 31 days. So the bull can get all the cows bred inside a month if I’m doing AI and want to try a 60-day calving season. But it still looks like I should be able to get them bred to the cleanup bull inside a month.