Not SQL-related, but in Excel I created a staff incentive scheme for a company using 4-4-5 ,and then had to 'adjust' every 3 or 4 years to bring the weeks into line. We then decided to switch to a '60 week year' where each month has either 4 or 5 weeks, with the Thursday deciding which month the split-week falls in. All monthly reports have 5 weekly columns. Sales targets for a 4 week month last year that's 5 weeks this year are 'stretched' to be pro-rata-ed and vice-versa. Week Number is an internal concept and runs from 1 to 59 or 60, with 'missing weeks'. it's easy to convert Week Number to Month as each month starts 5 weeks after the previous one. It automatically adjusts to 4-5-4 or 5-4-4, and occasionally 5-4-5.

No, I've no code available for you, but giving you food for thought about how to handle 4-4-5 type concept without the '364 days per year' limitation.

Regards

Brewmanz