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/june 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.

There are pros and cons to every alternative calendar. Just as there are pros and cons to the metric system, hybrid cars, and renewable energy. There is a short term cost to switching to better systems and a long term reward. The earlier we switch, the more reward we reap. Not saying that 13 months is the best alternative but the reasoning of systemic changes hinges on being willing to front costs that we know will be worth it in the long run. Our current one is not causing enough issues and it's upfront cost to switch is too high so we will likely not even seriously consider changing it for a long time. But we can still acknowledge that we should use a better system and that adapting earlier will only benefit us in the long run.