So I'm working on a nuclear physics problem and am looking at radioactive decay. The common unit used for very long decays is years within the literature. Is this the sidereal or tropical year? I want to use units of seconds but seeing as how these 20 minutes 24.5 seconds that differential will add up over time...

I would guess tropical but that's just a guess.

And on the same note, what about days? 24 hours? or 23 hours 56 minutes and 4.1 seconds?

So I'm working on a nuclear physics problem and am looking at radioactive decay. The common unit used for very long decays is years within the literature. Is this the sidereal or tropical year? I want to use units of seconds but seeing as how these 20 minutes 24.5 seconds that differential will add up over time...

I would guess tropical but that's just a guess.

And on the same note, what about days? 24 hours? or 23 hours 56 minutes and 4.1 seconds?

Bonus points for a source