Calendar

Each year is split into 15 months (5 seasons of 3 months each) and the 5 numbered days of Calibration that are not part of any season, month or week and are considered unlucky.
Each month is 28 days long, 4 weeks of seven days.
The days of the week are Sunday, Moonday, Marsday, Mercuryday, Jupiterday, Venusday and Saturnday (most people with some thought can identify these as named after the most powerful gods apart from the Elemental Dragons used to name the seasons).

The calendar seasons are Air, Water, Earth, Wood, Fire (followed by Calibration). Climatically the seasons vary across the world (three or four being the most common) but the hot of Fire is followed immediately by the cold of Air, with Earth and/or Wood typically being the growing season. The three months of each season are Ascending element, Resplendent element and Declining element. For example Descending Water is followed by Ascending Earth then Resplendent Earth.

While all of Creation agree on the structure of the year there is disagreement as to which year it is. Most call it Realm Year 768, but those less beholden to the Realm use an older dating system and call this the Year of the Mouse, Bronze era of the 11th epoch.

The New Moon is the last day of each month, making the first night when the first light appears on the moon. The Full Moon on Saturnday the 14th while the Waxing and Waning Quarters are the 7th & 21st respectively, the moon always rises as the sun sets except for Calibration when it does not rise - six days of no moon.

note the Calendar below incorrectly gives names to the days of Calibration, that is a limitation of the tool

Sources

1. Kingdom of Halta, pg 28