By the combination of the Scheduled Publish feature and the "No Future Posts" plugin, you can create posts at a specific date and release an artifact at a particular time.
Scheduled Publish (Tier 1 or higher plan)
Disable the "Auto Publish" feature
Install the "No Future Posts" plugin and publish the post at a future date.
Set publish date and time for Artifact
How to do with it
1. Disable the "Auto Publish" feature
Turn off this feature for the [Setting] page on Shifter dashboard.
Click the toggle switch to turn it Disabled.
See also: How to disable Auto Publishing Artifact
2. Install the "No Future Posts" plugin and publish a post on a future date
Start WordPress and login to it
Search and install the "No Future Posts" plugin on WordPress Dashboard; Or install it manually.
Then, activate it.
Write a post and set a future date to publish
Back to the top page and make sure the future post is published.
Generate an artifact (it won't be published, only generate)
3. Set publish date and time for Artifact
Scroll down to the "Deploys" section after generating artifact
Click the [Detail] button of an Artifact you want to schedule
Scroll down to "Scheduled Publish" section
Click calendar icon
The calendar will pop up, choose the date...
... and time you want to publish
Click [Schedule] button
The date is set
Back to the Overview page and make sure the Publish is scheduled
Wait for the time to be published.