Where do you hail from?
Most people prefer spring born calves, but there has been several studies done on fall born calves that demonstrated the return on investment is much higher, even with added feed costs. Most people don't care to increase feed costs and in the spring you have a lot of forage. In the fall, you run the risk of running out of forage or it is too hot to calve.
Google 'fall calving season research' and I'm sure you will find a lot of information.