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someguy3 ,

Hmmm now that I think about this a light year would be (should be) based on an average year, not what we observe in any given year.

365.2425 days. Different searches give different results but that’s what I’m going with.

EtzBetz ,

I would’ve said 365.25 days?

KISSmyOS ,

No, years divisible by 100 aren’t leap years, except if they’re also divisible by 400.

datelmd5sum ,

what is this, some sort of FizzBuzz calendar?

KISSmyOS ,

https://imgs.xkcd.com/comics/datetime_2x.png

EtzBetz ,

Oh right, I had some programming exercise about this, way back.

someguy3 , (edited )

They skip leap years every now and then. And then skip the skip. Etc. The rotation of the earth around the sun and the spin of the earth on its axis simply don’t line up into a nice number.

EtzBetz ,

Oh okay. Yeah I only have that rule of “every 4 years” in my head. I did some other programming exercise way back where we had some other rule, but I was thinking that it would end up being the same.

psud ,

You’d be imprecise for civil timekeeping, but spot on for astronomy

The civil rule is it’s a leap year if the year is divisible by 4, unless it is also divisible by 100 unless it is also divisible by 400

We saw the rules play out in 2000 (at least those of us over 23 saw it) which is a year divisible by 100 and by 400 so it was a leap year

Yours (and astronomy’s) is Julian style “if it’s divisible by 4”

I prefer the newer calendars, where there is no good mental calculation for leap years - it’s a leap year when the computer says it’s a leap year

IHawkMike ,

I almost certainly won’t be alive for it, but it’s funny to think about how confused people are going to be when 2100 isn’t a leap year.

callyral ,
@callyral@pawb.social avatar

idk, it feels more intuitive for it to be based on the mode (most common) year length (365) instead of the average year length (365.2425).

MBM ,

The boring answer is that in physics a year is just defined as the time it takes for the Earth to orbit the sun, they don’t care about calendars and leap years

psud ,

I would think that the best time period to use for a light year is whatever year definition has been used to date

Now let’s work on the best second to use for the light second

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