I'm not clear on your requirement, do you need to time intervals longer than 59 seconds? If so, how long? In order to time longer intervals, more than the seconds register from the RTC will need to be used.
The result of Macetech's conversion will be exactly the same as mine. His may be more efficient, I'm not sure that the modulo operator (%) is always the best in that regard. I should have a look into that.