My first playthrough took 101 days. I planned to improve the second one by 10%, down to 90 days. After considering that I could take Navigation instead of Fire or Air magic, I predicted an improvement to 85 days. In the end, I achieved 68 days, and I'm happy with the result. Regarding the 36 days, my opinion is: it's probably possible, but only if you involve one or two more main heroes to complete the quests. In my case (and, as I assume, for most players), there was only one main hero.