AW History screen

TrackerX55

Have a flag of some sort set in the AW history screen to indicate what wars are in the current season. Simply change the text from "X days Ago" to "Current Season" and "Out of Season" or "Last Season" depending on how far back the display goes. It'll make it easier for alliances who have people that only run half Season to see if they've met their minimum or not.

SummonerNR

Look at the scores, and look for when they no longer show the extra 50,000 points for a win. That should tell you where the separator was between current season and when prior offseason was. (pretty easy to tell whether that 50,000 is included in overall score just on main History Panels screen)

(unless your ally skipped entire offseason, but then the # of days ago will be a large gap instead you can see)