I can find all sorts of references for the year that the first battle of Moonbroth occurred (1610), but I don't see any reference to what season. My guess would be that the lunar government would avoid fire season (too hot), and they'd have trouble bringing in regular troops in Sea or Earth season (as their auxiliaries would not be available to support the invasion, due to being needed for planting and harvest. Storm Season might be out due to the air gods being strongest then... That leaves Dark Season. Possibly right after the harvest in Sartar is in. But at that time of year, Prax is at it's driest, and that would give the natives the advantage.
But is there an official date?
Young soldiers study tactics. Experienced soldiers study strategy. Wise soldiers study logistics.
- unknown