Oops, never mind. I thought I had to customize it, but I didn't!
This is what I was going to ask too!
Actually specifically I'm trying to do it within the Fiction template - want to keep the arc etc. Is that possible?
Hi, To change the calendar in the Fiction template to times relative to a Day 0 event, go to Timeline Settings (the cog icon). Under the Range tab, click Date. Next to "Style" there is a dropdown where you can pick "Daily (Day1, Day2). It then asks you to pick a zero date (the date in the standard calendar that you want to represent Day 0). Once you have done this, it will give you the calendar format you want, while keeping the other parts of the Fiction template. Jess