The Sherwood Calendar at a Glance

Year Published	1998
Days per Week	undefined
Days per Month	Option A: 23-33 Option B: 24-33 Option C: 27-28 Option D: 23-34
Months per Year	24
Base Year Length	668
Leap Days	1
Leap Day Position	Option A: mid-year Option B: end of 13th month (of 24) Option C: end of 19th month (of 24) Option D: end of year
Basic Intercalation Formula	2x668 + 3x669
Extended Intercalation Formula (\ denotes integer division)	undefined
Mean Length of Calendar Year	668.6
Base Astronomical Year	Vernal Equinox
Accuracy	106 years
Cycle of Perpetuity	undefined
Mean L_S of Beginning of Year	0.0
Year Count Start	undefined
Epoch (CE)	undefined
Epoch (JD)	undefined

Note:

Options A, B, and D are examples of Asymmetric Vernal Equinox Martian calendars, which generally have the following characteristics:
- Divide the Martian year into 24 months of unequal duration, encompassing approximately equal arcs of the Martian elliptical orbit.
- Retain the seven-day week.
The Option C calendar is similar in structure to the Darian calendar, but was developed independently. The 27-day months and the leap day are placed differently.
Options C is one of several Symmetric Vernal Equinox Martian calendars, which generally have the following characteristics:
- Divide the Martian year into 24 months of approximately equal duration.
- Retain the seven-day week.
- Begin the year on the vernal equinox
- Place the leap day(s) at the end of the year.
Other types of 24-month calendars are:
- Symmetric Double Gregorian Martian calendars
- Symmetric Summer Solstice Martian calendars

	Martian Calendar Anton Sherwood
	Option A
	Option B
	Option C
	Option D
	Martian Time
	Martian Time Survey 2.2