One season consists of five campaigns, and each campaign is two weeks long (with an offseason between seasons). A new campaign will begin every other Friday... you can see how many days are left in the current campaign by looking at the upper-right corner of the war map
You need to manually deploy troops on the war map (as you first did for the "Cry Havoc" trophy) in five different campaigns. That means getting this trophy will take a full four campaigns plus deploying on any day of a fifth campaign... the campaigns don't have to be consecutive either.
And yes, manually deploying troops during an offseason does count towards this trophy. I unlocked this trophy by deploying in offseason and the first four campaigns of a new season.