Our countdown timers are intended to countdown to a specific date and time. Each timer has one end date and time associated with it.
We do offer an API that does allow some flexibility if you can add an end date time on the fly, but this is only an option if you can generate a token or calculate the end date time on your end. Unfortunately this is not possible when using a email marketing service such as MailChimp. Follow this link for more information on our API.