Times and durations are stored as dd:hh:mm:ss
The following functions work on times or strings to return a time:

TIME(hh:mm:ss) or  TIME(hh:mm) returns the time specified as a time

MINUTES() returns number of minutes eg. MINUTES(“12:56:00”) = 56

SECONDS() returns number of seconds eg SECONDS(“12:56:23”) = 23

HOURS() returns number of hours eg. HOURS(“12:56:00”) = 12 

DAYS() returns number of days DAYS(“15:12:56:00”) = 15 

For example, to calculate 1 min 30seconds from now, you can use Audience.sender.later = NOW()+”00:01:30”