Emma here from Shopify. At this time, you cannot edit orders in Shopify without the use of an app such as Edit Order by Cleverific, which allows you to change customer shipping or billing info, adjust pricing, add or remove SKU's and line items on any customer order. Even with the use of such an app, I'm afraid it doesn't look like you can change the date of an order. You could try reaching out to the app developers to enquire about whether or not this could be achieved with their app. Let us know what you find out!
In the meantime, I'd be happy to pass along a feature request for you. Our developers are always open to suggestions and we truly value your feedback. If you wouldn't mind sharing how this feature would improve your business, and why it's important to you, I would love to share that information with our team.
All the best,
Emma | Shopify Support
If you are still looking for a solution to this take a look at how our app, AirPower, enables you to create/update draft orders from Airtable. You can see the sample Airtable base to do this here, and we have a help article on how to set this up - How to create and edit Shopify draft orders from Airtable . You can easily update the date of a manual order in your Airtable, and our app will reflect that in Shopify.
I would like to be kept up to date regarding the ability to back-date orders. I am using Shopify to create many manual orders, in addition to having customers place orders through my online store, and often the manual orders need to be backdated. please keep me in the loop!