Making my homebrew world to have 450 days per year.   Which would be 10 months with 45 days per month.  5 weeks per month.  9 Days a week.  But anyone know how many hours per day and seconds per minute for this?  

I would keep it at 60 seconds per minute. You could make the hours per day anything you want. For example, I’m partial to a 30 hour day and 8 days per week with 4 weeks per month and 12 months per year. That comes out to exactly 32 days per month, and exactly 374 days per year. I know someone else who decided their world has 26 hour days.

However, some spells have durations that last 8 or 12 hours because they were written under the assumption that a “day” is 24 hours, so that’s ⅓ or ½ of a day. Just something to be aware of.