I've been using yWriter, which is great, and have just downloaded Storybook to see if that's better, but neither one of them entirely supports what I'm looking for.

For one thing, they don't allow for custom calendars. Does anyone know of any writing software that lets you fill in your own day, month and year names?

They also don't seem to offer the ability to create custom fields, in which you could detail each characters special powers, if they have any, and things like that.