I guess there's a bit of a 'philosophical' question here: is a day 86400 seconds, or is it one rotation of the Earth on its axis?
Or the amount of rotation required to point towards the sun again, which is slightly more than one rotation (remember, we orbiting while spinning, so noon to noon is a bit more than 360°). This is a solar day; your definition is called a "sidereal day" (and is a real thing, too).
(And the solar definition has issues, too, which leads to, e.g., mean solar time…)
What I do not understand, considering the above (Julian years and days have been used for a long time in respectively paleontology and astronomy, haven't they ?) as well as from TFA :
> Abolishing leap seconds will be helpful for users that have very tight accuracy requirements. UTC is the only timescale that is provided by national laboratories in metrologically traceable manner, i.e. in a way that provides real-time access, and allows users to demonstrate exactly how accurate their timekeeping is.
> TAI is not directly traceable in the same way: it is only a “paper” clock, published monthly in arrears in Circular T as a table of corrections to the various national timescales. (See the explanatory supplement for more details).
So, what are we waiting for to just have both scientific time and civil time being broadcast separately (and scientific time with more precision and frequency, not less !), and then you use one or the other as appropriate ?
That would require either doubling the radio frequencies (and other channels) used for time broadcast, or changing the transmission format to include both (so not really separate). Some systems actually broadcast the current leap second count along with UTC, so TAI can easily be derived. Of course, that presumes that UTC and TAI keep being related by a leap second count. Going to fractional seconds of delta would again require changing protocols and data formats.
In addition, we’d presumably still like a civil-time second to be the same as an SI second, and not go back to the “rubber seconds” of the 1960s. But how then would we handle the fact that the solar day isn’t exactly 86400 SI seconds [0]? Add/remove some fractional seconds at the end of each civil day? That might cause even more issues in software than leap seconds.
Right, leap seconds it is then, but note that that and minutes/hours/days/years here is something that is only required for human interfaces, while the computer itself only cares about a monotonically increasing seconds counter on its internal clock, which is required to be stopped/started/re-adjusted once in a while anyway.
Oh, and conversion between scientific and civil time is then the job of local polities, which they do for timezones anyway.
The current answer is everyone uses UTC, and they keep synchronized by observing the one universally disseminated time, which is UTC.
You use and synchronize to the same time standard as the world-metrologists do (TAI), the whole issue is that that's not the one that is being disseminated as the article and I already pointed out.
UTC is a (strange) compromise between both: ticking SI seconds like TAI but being kept within 1 second of UT1.
Timezone bands are massive. If they were perfectly straight (they aren't) then civil time in any one place would be off by up to 30 minutes in either direction, depending on the location. In reality they line up with political entities instead, creating even larger discrepancies (with the extreme case being China, where some regions are hours off).
Compared to that, a second every couple of years is completely irrelevant.
1 sidereal day is about 4 minutes shorter and the time it takes for the stars to be in the same position.
As far as I know, unless you're doing certain types of astronomy, you're using solar days.