Since Mone's orbit was stabilized during the foundation of the Ottansey colony, the yere dovetails nicely with revolutions of Mone. The yere is divided into ten twams of 29.850 days each; each twam is two mones of slightly less than fifteen days each.
The inevitable simplification gives eight twams of 30 days and two of 29; every second yere is a leap yere with nine 30-day twams.
The yere begins with new mone immediately before the vernal equinox. Then each twam progresses through the same cycle of monation, with new mones at midnight of the 1st/15th days, first quarter at 3.75/18.75 days, full at 7.5/22.5 days, and last quarter at 11.25/25.25 days.
Rather than weeks, each twam is divided into four periods of waxing and waning mone: Greater Waxing of 8 days, Lesser Waning of 7, Lesser Waxing of 7, and Greater Waning of 8. When a twam has only 29 days, the cycle is slightly changed: Greater Waxing (8), First Waning (7), Lesser Waxing (7), and Second Waning (7).
The "days of the week" cycle thus repeats in this fashion:
Greater Waxing
1 - Darkday
2 - Starday
3 - Windsday
4 - Midwax
5 - Grunday
6 - Kinday
7 - Sunday
8 - Fulday
Lesser Waning
9 - Shinday
10- Windsday
11 - Midwane
12 - Grunday
13 - Halday
14 - Tweenday
15 - Dimday
Lesser Waxing
16 - Darkday
17 - Starday
18 - Windsday
19 - Midwax
20 - Grunday
21 - Sunday
22 - Fulday
Greater Waning
23 - Shinday
24 - Wyrmday (dropped in Whitmon & Dixia)
25 - Windsday
26 - Midwane
27 - Grunday
28 - Halday
29 - Kinday
30 - Dimday
Specific dates are usually referred to by day-names: Wyrmday and Tweenday occur only once in each twam; Windsday and Grunday occur four times and are distinguished by "first," "second," "third," or "fourth." Other days, occuring twice each, are designated as "first" or "second" on Dakan and Tumaden, and as "greater" and "lesser" in Ladamar.
The Mids -- Midwax and Midwane -- are days of rest, equivalent to Terra's Sunday.
The twams are named as follows:
Spring
1 - Niwyar (30 days)
2 - Grenmon (30 days)
Summer
3 - Dixia (29 days/30 leap yere)
4 - Kaalon (30 days)
5 - Melemon (30 days)
Autumn
6 - Hwatmon (30 days)
7 - Erst (30 days)
Winter
8 - Brandym (30 days)
9 - Whitmon (29 days)
10 - Yarnd (30 days)
Vernal equinox: First Darkday, Niwyar
Summer Solstice: Tweenday, Dixia
Autumnal Equinox: First Darkday, Hwatmon
Winter Solstice: Tweenday, Brandym
To convert:
Ottanseyn Yere = ((Year CE - 2970)/1.09)+817
Year CE = ((OY-817)*1.09)+2970