You can use BuiltWith to create reports of when a web technology was first implemented. For technologies which have yearly contracts you can use this information to determine if an implemented technology is due for renewal.

To find websites with expiring technology contracts customize a report and set the “First Detected” date to the preset of “Approximately 1 Year Ago” –

Expiring Contracts

This will create a report that lists technologies that were first detected between 13 and 11 months ago, providing you an opportunity to potentially find new customers in this renewal window.