The short answer is that you may not change the check date. We've heard this request multiple times, and appreciate your concerns and needs as a business.
When you create an eCheck, it is date and time stamped as a security feature. There is not a way to edit the date on a check because of this date and time stamp.
Note: We are looking at ways to make scheduled payments an option.
If this is a feature you would like to see, contact our Support Team (contact information in the footer of the website pages, the eChecks Help Center and all system-generated emails). Your feedback helps us prioritize feature requests.