The World of Mystery has several calendars but the one used by civilised folk worldwide uses a system somewhat like the so-called “tzolkin” Mayan calendar. Tzolkin is a confected term invented by mainstream archaelogists but the interlocking cog type calendar it is applied to is real.
In the case of World of Mystery the cogs of the calendar are:
Colour – Zodiac
There are 13 months, simply named by numerical order. Each is 30 days long. Each month is also composed of three tendays – simply “weeks” of ten days each day of which is simply named by its position or absolute number in the month – Fourteenth Day of Eighth Month, or Fourday of Second Tenday, Eighth Month.