Time.h rollover after 49.7 days
As long as the date is before 2038, and your code calls one of the time functions at least once every 49 days, rollover won't affect you. 

Internally the library uses Unix epoch time. Every time you call a function it checks to see if 1 or more seconds have past since the last time it was called and then updates the epoch time accordingly. Only for this check it uses millis(). And in only checks the difference between the last call's millis-value and the current millis-value, and rollover has no effect on time differences (as long as they are less that 49 days).