While developing themes, it’d be useful to be able to backdate blog posts, especially when building archives.
In the meantime, someone let me know if this is possible now. I have no way of knowing if the theme I’m developing works until September 1st. 
Do you mean something like this?
Yes!! Now is it possible to do that in bulk?
Say – client wants to import 300 .txt files with dates.
(Also, now I know my theme does not, in fact, work. Thanks!)
If it’s something that big, you probably want to use the API or import posts - see Migrate an HTML blog to Ghost
It’d be great if the calendar for choosing the post date allowed you to type the date directly in the field rather than manually moving one month at a time into the past. I’m currently bringing over a bunch of old posts from a crippled Movable Type blog, and it takes ~130 clicks to get where I need to be for backdated posts in 2006 and 2007. It’s a little maddening. (I hope I’m just missing something obvious!)
I’m running into the same issue. Currently migrating and frustrated that I can not simply type in the date. I’m trying to think of a way allowing this would negatively impact any UI/UX decisions the team wants to maintain but I can’t think of any way it would.
Please add this it seems like an easy fix (IMO)!
It’s possible to type in the date fields as of Ghost 3.3.0.