Custom Form : Insert a Date picker to the checkout form in Coding and Customization Posted March 3, 2020 · Edited March 3, 2020 by Trystan Ho ! I see you are the developer behind the Date picker extension. I bought it earlier this day, I'm currently waiting for the extension to arrive in my mailbox. I just find it ridiculous that Squarespace doesn't come with basic HTML editing for the form content. It's painful if we want to extend our websites. For the store itself, the customers have to give a date of location for every product they are buying. The default squarespace date form is not very intuitive, so a need to get a date-picker for it.