There's an article from 4th August on the Ghost blog that states:
You can now schedule posts in Ghost to be published at a predetermined date in the future! This is one of our most requested features of all time, so we're really happy to finally have it out in the wild.
It works just as you'd expect: Once you set a publication date in the future, you'll notice the publish button change from "Publish Post" to "Schedule Post". Hit that, and you're all set.
One thing you need to do though is to set the time zone, which is in Settings/General. I didn't know that and in fact my time zone was set to an hour earlier than the correct time zone.
I didn't set it so I don't know how it came to be set that way. It happened when my Web host updated Ghost to 0.9 about a week ago. Prior to that it was not possible to schedule posts, and I didn't realise there was a setting that I now needed to check.
I didn't notice there was a problem when I hit Publish , but when I went back to the post to edit it, I saw Save Draft rather than Update Post.
When I pressed the disclosure tab I could see an option to schedule the post - but of course, the post had already been published.
When I looked at the scheduled date, I saw it was the date and time the post was published, which was of course now in the past.
When I looked at 'Content' and the list of posts, the post was marked Published in an hour, which was strange syntax and seemed to suggest a future time.
When I refreshed the page it said Pubished in 54 minutes, and it kept on counting down until, after an hour it said Published a few second ago.
And then when I clicked the edit button I could see Update post.
So there was a mismatch between what Ghost thought the time was and what my site thought the time was.
The timezone I am on with my web host is 'the default cloud hosting time zone that is London/Europe time stamp’.
Finally, after asking on the Ghost Slack channel and my web host, I saw that I needed to check the time zone in Settings/General.
Once I did that, everything was fixed.