You can use the parseDate function.
For example, the requirement is to check if a date (in a data cell) is 2 days past the current date. Sample value of cell = 2016-09-03 07:25:00 and current date is September 5, 2016. Then you can set a rule:
where 172800 is the epoch equivalent of 2 days. Sample output:
You just need to modify the string format in the parseDate function if you have a different date format. This can then be compared to the now() function which represents the current timestamp in epoch format.
You can find the full set of time formatting codes used in the rule block here.
The reverse function is printDate which converts epoch timestamp to any format readable times using the same time formatting codes.