It is possible to append a countdown clock to countdown to an end time based on the time of send or another variable.

Example 1: Show an offer valid for 48 hours from email send time
Example 2: Show an offer valid for 30 days based on time of signup

How?
Create a clock template and countdown Tag as usual – give the clock any end date in the future.

E.g.
https://img.kickdyn.com/2690/66muQOL9OkVBuKXD1Fff/imgancnt.png

 Rearrange the tag in the following format:
 
https://img.kickdyn.com/imgancnt.png?c=2690.66muQOL9OkVBuKXD1Fff&cntdate=

Add the merge code from your ESP to populate the tag, the following date formats are accepted:

yyyy-mm-dd
yyyymmddhhmmss
mm/dd/yyyy

e.g. time of send =
%YEAR%%MONTH%%DAY%%HOUR%%MINUTE%%SECOND%

Then add the number of hours required to the end of the Tag e.g.
https://img.kickdyn.com/imgancnt.png?c=2690.66muQOL9OkVBuKXD1Fff&cntdate=%YEAR%%MONTH%%DAY%%HOUR%%MINUTE%%SECOND%_48

Here’s an example of a post send Tag:
https://img.kickdyn.com/imgancnt.png?c=2690.66muQOL9OkVBuKXD1Fff&cntdate=20161013113300_48

Tip: if you use a date stamp and not a time stamp, the clock will count down from midnight on the specific date merged.