In our calendar, the months would approximately match:
The imperial calendar has a year divided into 12 months of 30 days, plus a short span of 5 to 6 days that are outside of any month, placed around the summer solstice.
The month’s are roughly spaced so that the full moon is around the 1st of the month, and the new moon is around the 16th.
In many places in the empire, these days are generally considered to be outside of general reckoning. People do not work, and instead a week-long festival is held, with offering to Shadari, Abaredae and/or local gods. Though this period isn’t part of a month, and doesn’t really have an official name, sages will often refer to the days as the 1st, 2nd, 3rd, etc. of the Festival.
The twelve months, from the festival onwards are:
Late Summer: Judgement, Craft, Harvest
Early Winter: Books, Remembrance, Prayer
Late Winter: Hearth, Stocks, Growth
Early Summer: Planting, Law, Mercy
The imperial calendar starts at the end of the god war and founding of the empire, which is also denoted as the end of the Age of the Ancients, and the start of the Age of Man. Unless otherwise denoted, all dates are assumed to be in the Age of Man.