It's a 13 month calendar with 28 day months, the 365th day would be special new year's day and not part of the count. It has many obvious advantages:
- All months have the same length
- All months start on monday
- All years start on monday but new years day is still a day off (and a long weekend by definition)
- Paydays would always be the same weekday
- Financial Quarters (three months and a week) would always end on fridays
- American style holidays (the third Thursday of...) could be given a date
- Menstrual cycles would be easier to remember
Its disadvantages are rather limitations shared with the Gregorian calendar:
- Since the lunar and solar calendar have by nature different periods, the lunar calendar would be out of synch with the new calendar.
- A 365 day calendar would still need leap years (The earth would still take an extra 1/4 of a day complete a revolution around the sun). The guys at the "Calendar Change Splinter Group" propose a 13 day addition every 52 years but in my opinion having the solstice, equinox and other astronomical phenomena move by as much as 13 days is not acceptable. In fact any correction more than four years apart is unacceptable.
For getting rid of leap years we need to have 6 unaccounted hours per year. This obviously can not be done at once since the sun would rise at noon (that is why in the Gregorian calendar they are accumulated over 4 years, a whole day correction doesn't affect the time-of-day clock). Half an hour could be added every two months, but this being a 13 month calendar one year it would be the odd months and the next one the evens. It also is unrealistic to expect people to adjust their clocks 6 times a year.
For the moment my calendar will have 48 hours new year day every four year, maybe in sync with the olympic games®