Time arithmetic is always fun. The original ANSI SQL standard had the intelligent distinction between year-month intervals and date-time intervals for just thi

Time arithmetic is always fun. The original ANSI SQL standard had the intelligent distinction between year-month intervals and date-time intervals for just this reason - you have to watch for errors to choose how to hand out-of-bounds conditions (e.g. "myDate + 1 units year" when myDate == 2016/03/29).