Calendars and Time

A moon (lunar) month is 28 days. There are 13 lunar months in a year, totalling 364 days. Adding 1 more day (365 days) makes a  year, hence the expression common in folk tales of  'a year and a day'.

Alternatives have been proposed to the current Gregorian (Western/Christain) Calendar to even out the irregularity of the months. However there are issues around religious observance days, the need to reconcile academic terms, implications for the working week (shift rotas, weekends), and peasant economies where there is not enough need for permanent shops and trading is done through several interlocking market cycles, each based in a different village, not to mention finding acceptable-to-all names for the weekdays and months.

• Perpetual 364 day calendar plus 1 day per year.
• Perpetual monthly international fixed calendar: 13 months of 28 days plus (a) New Year's day every year and (b) Sol day every leap year. Every date is fixed on the same weekday (e.g. 1, 8, 15 and 22 are always Sundays).
• Perpetual trimester calendar (World calendar): Months are 31, 30, 30 in each trimester (3 months). Every date falls on the same day of the week (Jan. 6th is always a Friday, Feb. 6th is always a Monday). Dec. 30 is followed by World's day every year and Jun. 30 by Leap Tear day in leap years (neither have a day of the week).
• Calendar reform.

Interesting fact: The Plaiades (also known as the Seven Sisters): the only constellation noted and named by every culture on earth, past and present.