An interesting question from Stack Overflow asks “Why is MySQL’s maximum time limit 838:59:59?”
The official reference at http://dev.mysql.com/doc/refman/5.7/en/time.html says
TIMEvalues may range from
838:59:59. The hours part may be so large because the
TIMEtype can be used not only to represent a time of day (which must be less than 24 hours), but also elapsed time or a time interval between two events (which may be much greater than 24 hours, or even negative).
TIME values were always stored on 3 bytes in MySQL. But the format changed on version 5.6.4.