Not sure if it's intended for SW seasons but in RoG the Winter and Summer seasons randomly last one day longer than usual. Discussed this on reddit earlier and it seems like there's a fix for it in DST already. Until then we'll have Summer last 16 days out of 15.
SW seasons also have unusual lengths. Instead of the 20-15-20-15 that was in RoG, they last 20-16-21-16. That doesn't seem right.
Just survive any of the "short and difficult" seasons in RoG or play a normal game in SW. The mod "Combined Status" helps to keep track of the season days.