- #1
swampwiz
- 571
- 83
I know that the definition of the second is a precise value based on some natural oscillation of a certain isotope, with a day being exactly 86400 (i.e., 60 x 60 x 24) seconds - whether or not the actual average day is a little different (and hence the leap seconds we've been getting lately.) But I am wondering what is the exact definition of a year as a unit of time, that used for radioactive decay and the light-year. I figure that it is based on a tropical year (i.e., time between a pair of vernal equinoxes) or some epoch, but what exactly is the value in number of days. I can't seem to find this anyone on the 'net. Thanks