If I had an automated system that pays my bills, but the website where I pay them won't tell me when the next bill will be available. What is a good approach of predicting the date of the next bill? I don't see a regression model here as a good approach. I believe it's better to get a simple statistical mean or median between bill dates in days, and then guess the next bill date as: nextBill = lastBillDate + mean. Is that the right approach?
I don't know your data, so I can't say if your approach is good or not. But your approach does not cover weekdays. So I would apply time series analysis methods predict the service date.