The calendar is a good bug fix, but it also provides an easy way to beat the levels, because when you click the calendar, theenemies do find a new path, but they also stop attacking, while your own units do not. this means rapidly clicking this button will mean the enemy will never attack, proving with an easy win.
uh sometimes the enemies walk right past the helicopter and don't attack it at all, and they don't walk back into the screen... so it makes it impossible to kill all the enemies
In hindsight, I wish I had.