Thank you for reaching out to the API Support team here at Constant Contact.
The original issue reported here has been resolved. In testing this myself I was able to limit my results to only contacts modified after a specified date and time. You may be having an issue that is account specific or perhaps there may be something in your contact data.
So that we can best assist you, please email email@example.com directly with information about which list or call you are attempting to make. Since you are seeing the issue with our API Tester as well, please include the Request URI and Headers shown there in your email.
API Support Specialist
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