Right now, a month is 4.345 weeks and 30.4167 days. it makes scheduling and budgeting kind of a nightmare. in a 13 month calendar, each month has 4 weeks exactly and 28.096 days. the 0th of january/july isn’t a day of the week like Sunday, it’s just an extra day. That makes it a lot easier to call it a holiday, pay out like it’s bonus time, add at the end of calculations, etc. I think it’s actually easier to grasp conceptually than our current way of handling leap years. The main benefit though is that even if you did include 0th days as a day of the week you would still only have ~4.1 weeks per month. The decimals are much lower and as a result much less frequent. 30.4 days per month is atrocious, it’s basically a coinflip. Doing any kind of math on our current calendar system is a giant pain and would be much improved with any system that can lower that decimal value.

As for practical benefits for the majority of folk that don’t make budgets or deal with scheduling, Every month now starts on Sunday and ends on Saturday plus we get a new holiday, neat. Every 16th, for example, is now a Monday. Honestly, everything about it sounds better to me and it’s not even my favorite alternative calendar.