Require a date field entry to be after a date entered in another date field

That's not possible with Airtable forms currently I'm afraid.  You can prevent them from keying in a date before today, but can't prevent it off of the other entry in the form.  Perhaps you could set up an automation that'll email the person that submitted it if the return date is before the start date?

If you're open to third party solutions, you could try Fillout.com for this too, which has this functionality I believe https://www.fillout.com/

@Fire315 

Airtable does not offer dynamic validation on forms.

Airtable DOES let you do that — in a very halfhearted & uninspiring way — with interfaces or the data layer by using automations to clear out the wrong date, or by creating a formula field that presents the user with an error message. But there is absolutely no way to do any of this using forms. And there is also no way to prevent the user from typing in any date that they want.

However, the great news is that you can get EVERYTHING that you want to do (and much more!) by using Fillout’s advanced forms for Airtable.

Fillout is 100% free and offers hundreds of features that Airtable’s native forms don’t offer, including the ability to have dynamic date validations (or dynamic validations of any kind), the ability to prevent submission of a form if it doesn’t meet your required criteria, the ability to display conditional error messages on forms, the ability to update Airtable records from a form, the ability to display Airtable lookup fields & rollup fields & attachments & formulas on forms, dynamically & conditionally filter linked record fields by any values that you would like, perform math or other live calculations on your forms, accept payments on forms, create multi-page forms with conditional paths, create new linked records on a form, display as many fields as you want to see in a linked record selection list (including attachments), connect a single form to dozens of external apps simultaneously, limit the number of linked records that can be chosen, set advanced field validations & limitations, upload an unlimited amount of attachments simultaneously, add CAPTCHAs to your form, add choice matrixes to your forms, direct integration with hundreds of apps like Calendly & Google Maps on your forms, and so much more.

Hope this helps! If you’d like to hire an expert Airtable consultant to help you with anything Airtable-related, please feel free to contact me through my website: Airtable consultant — ScottWorld 

Hey @ScottWorld, 

I really love your approach to replacing the form with workflow and automation! This is what I do also, and I love it! 

Bur we miss the feature for people outside of our Airtable 😞 

Yes, I agree with you that it would be nice if Airtable offered these capabilities for external users!

thank you all for great suggestions! For my purposes, leveraging what I can use within Airtable would be enough. But I'll look into using an external party solutions when there is a need.