it's not exactly one year, hence why every 4 years we have a leap year to correct for this.

why do you think we have leap years?

Leap years bro

It's because God used american units when he created earth

>>4322643
>>4322644

We have leap years, because number of days in a year is not integer
Which absolutely does not explain why Earth supposed to take longer than 1 year to go around the Sun

Wikipedia runs on an old Pentium I with FDIV bug

what correction do we use in total? i know that:
every 4 years we add 1 day.
every 1000 years we dont add that day becasue 1 day every 4 years overcompensates.
anything beyond that?

>>4322664
>>Earth supposed to take longer than 1 year to go around the Sun

This, how come it takes more then 1 year to go around the sun? Isn't that the definition of a year?

>>4322673
to keep it simple a year is defined as 365.25 days.

>>4322669
You know wrong. The leap year is applied every 4 years except those divisible by 100 but not 400.
That makes a correction of 1 day every 133.33 years

>>4322694
sorry, i noticed it right after i post that. that i had like 5 extra days per 1000 years.

Because there is a difference between sidereal year (Earth returns to the same space position relative to Sun) and tropical year (Earth axis returns to the same angle relative to the Sun). Tropical year is more relevant to the everyday life because it corresponds to the seasonal period. Sidereal year is more relevant to the physics, because it's the rotation period of the Earth on the orbit around the Sun.

Tropical year is shorter by ~20 minutes because of Earth axis precession. 1.000017421 is the length of sidereal year expressed in tropical years.

>>4322682
>>4322673
>>4322664
IIRC a year is 365.25 days, rather than the orbital period.

IMA CHEYEKNEE

I DOWN UNASTANA LEAP YEAH

>>4322737
Now that I looked for the second time, it's not quite right. That would be ~1.000038, not 1.000017. Some moron divided it by 365.25 instead of 365.2422

Therefore: 1.000017421 is the length of precisely calculated sidereal year divided by the arbitrary year length as defined by Emperor Julius Caesar in the year of our Lord -46

>>4322635
Think of it this way, OP;

You know how the moon has a rotation period of 1 month (and I mean rotation, not revolution). It's part of the same principle.

While we're revolving around the sun, there's a slight rotation occurring as well. The length of 1 full rotation on earth *technically* isn't 24 hours, because we don't actually measure days by how long it takes the earth to spin in a full circle. We measure how long it takes before it faces the sun again.

>>4322656
>>4322664
>>4322673

The reason it seems arbitrary is because we wanted it to be as less arbitrary as possible. As a global society we are always trying to tie certain, otherwise arbitrary, metrics to natural phenomena. So, we standardized the second as:

>"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom."

Then we decided minutes and hours should operate on the sexigesimal system, because it has the most divisors. Well, actually that happened before the standardization of a second, but that's irrelevant. After all of this, we tied the length of a single Earth day to be one complete rotation. At least that what it would've been if it the rotation rate were constant, which it's not. So you have, a solar day, which is basically just the average rotation time, and then you have the stellar day which is about 4 minutes less.

+stellar day - an entire rotation of a planet with respect to the distant stars
+sidereal day - a single rotation of a planet with respect to the vernal equinox
+mean solar day - average time of a single rotation of a planet with respect to the sun as the central star

So, we just decided to make a day 86,400 SI seconds.

BUT, we're not done yet.

To keep the civil day aligned with the apparent movement of the Sun, positive or negative leap seconds may be inserted.
A civil clock day is typically 86,400 SI seconds long, but will be 86,401 s or 86,399 s long in the event of a leap second.

tl;dr dates are pretty fucking arbitrary because humans aren't cool enough to completely master it.

>>4322814
I've memorised that light travels 3.26cm per transition between hyperfine ground states in Cs-133. Probable one of the most objective measures of stuff I know of.

>>4322762
>Anno Domini
>Negative Years.

>>4322791
>You know how the moon has a rotation period of 1 month (and I mean rotation, not revolution).

Jesus, are you fucking 12?

How could you not know that the moon is tidally locked to the Earth? Haven't you ever heard of the expression 'dark side of the moon'?

OP is right.