From what I could gather (and it is so little yet so hard to gather it all) I think for now, everyone from the cast will receive 14 days. Since these 14 Days are the Prologue and they serve as context story for us, before we resume our story in Present. However, what happens after everyone has gotten their 14th Day is still beyond my gatherings, but will resume whenever I get the chance. For now, we have to expect a canon event on Day 13 on every route, since choices of great importance take place on the same specific day for every route.