That's a really hard question. We already know that “days” is just a meassure, and “days” are different depending of the planet. read more
Well one Krypton year is called Ahzmet and is roughly 1.3879 years(2). read more
The pre-New 52 version of Superman was re-introduced in the comic book series Superman: Lois and Clark and for a time Earth had two superheroes each called Superman. The older, more mature Superman remained on Earth after the younger Superman died in Superman vol. 3, #52 (May 25, 2016). read more
Since 18 Kryptonian years is about 25 Earth years, then there were approximately 2.3 Earth years between the two events. The exact number of days between February 29, and June 16 two years later, is 838 (or 2.294 years). read more