TopCoder - SRM 144 - Div 2 - 200 Pt

From Single Round Match No. 144 of TopCoder's Algorithm Competition:
Write a method whatTime which takes an int representing the number of seconds since midnight on some day, and returns a string formatted as H:M:S.
(Full problem specification is copyright TopCoder; and, can be found in the TopCoder problem archives.)

Solution.
Unit Tests For Sample Data.

This problem was used as the Division 2 200-point problem. Being a 200-point problem, it's very straightforward; and, there are no real "gotchas" involved in the solution.