The very fact they are there, still used, and so on, contradicts "unnessary [sic]". Sure, it might be outdated now, or technically better alternatives might be there.
But, in the end, software that deals with "The Real World" is going to be a complex, illogical mess. Because the real world is a complex, illogical mess. We could make a time that is global, counts resonant frequency of atoms. While technically superior, I will continue saying "The job took me 3h25 minutes" and not "The job took me 113,066,170,771,000,000 cycles", or even "The job took me 113066 Tera-cycles." or such. Messy, illogical and complex is often simply more practical. If only because "everyone does it that way".
And we're going to say "let's do this a day from now", leaving the software to decide whether that's 24, 23 or 25 hours from now. It could be any of those things, depending on where it was said and the DST changes for that timezone.
Or conversely, is a specified instant considered "tomorrow"?
I generally consider "tomorrow" to be an interval and not an instant. It is ambigous how large of an interval it is and how far in the future it begins.
"tomorrow" in the real world is also surprisingly complex.
I once built a calendar and reservation system for a theatre that did movies, theatre, concerts and parties. A party that starts Friday at 22:00 and ends at 1:30 doesn't end "tomorrow" in people's minds, it ends Friday night.
(And a party, concert or movie that technically starts Sunday, 00:15 still has to show up on Saturday night 00:15, because that's how everyone looks for it)
The very fact they are there, still used, and so on, contradicts "unnessary [sic]". Sure, it might be outdated now, or technically better alternatives might be there.
But, in the end, software that deals with "The Real World" is going to be a complex, illogical mess. Because the real world is a complex, illogical mess. We could make a time that is global, counts resonant frequency of atoms. While technically superior, I will continue saying "The job took me 3h25 minutes" and not "The job took me 113,066,170,771,000,000 cycles", or even "The job took me 113066 Tera-cycles." or such. Messy, illogical and complex is often simply more practical. If only because "everyone does it that way".