The world generally uses the Dwarven calendar.
The current date is 23 Flint 1167.
The dwarven calendar is based on 8 months of 32 days each, giving us 256 days in a year:
Generally, the seasons change on month boundaries. Spring begins on Granite 1 with the new year, Summer begins on Basalt 1, Autumn begins on Marble 1, and Winter on Sandstone 1.