What is the easiest way to figure this out?

Question

5 yrs 21 days 4 hours 32 min 17 sec
_ 2 yrs 93 days 7 hours 47 min 24 sec
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Answer 1

Change the way you write the upper number from:
5 yrs 21 days 4 hours 32 min 17 sec

to:
4 yrs 385 days 27 hours 91 min 77 sec

Then you can subtract
2 yrs 93 days 7 hours 47 min 24 sec column by column,
without getting negative numbers in any ategory.