Make the precision of display ages and dates/times consistent, regardless of their age

Question

Currently, the way that the ages and dates/times are displayed is inconsistent, and it would be beneficial to make them consistent:

Age	Display	Example	Precison	Relative precision
0 seconds <= age < 4 seconds	just now	asked just now	3 seconds	Fair
4 seconds <= age < 1 minute	{x} seconds ago	asked 24 secs ago	1 second	Excellent
1 minute <= age < 1 hour	{x} mins ago	asked 22 mins ago	1 minute	Fair
1 hour <= age < 24 hours	{x} hours ago	asked 1 hour ago	1 hour	Poor
24 hours <= age < 48 hours	yesterday	asked yesterday	1 day	Poor
48 hours <= age < 72 hours	2 days ago	asked 2 days ago	1 day	Poor
72 hours <= age (this calendar year)	MMM dd "at" H:mm	asked Sep 10 at 8:03	1 minute	Excellent
72 hours <= age (not this calendar year)	MMM dd 'yy "at" H:mm	asked Dec 10 '20 at 7:06	1 minute	Excellent

I'm aware that, on a desktop device, it's possible to use the workaround of hovering over the timestamp of pretty much any event to get the ISO 8601 UTC date and time, e.g.

but on a mobile device this is not possible, as these feature requests from 2013 and from 2019 state. Going to the timeline for a post then toggling the date/time display format works on all devices, but is even more of a faff.

I posted a bug report in Review queue workflows - Final release where the dates reported in review are different to how they're reported in the posts themselves, but the behaviour in review is arguably much worse (all events less than 24 hours old are reported as "today") - I'm sincerely hoping that that's not the way that dates/times will be reported in future.

Sometimes (often for newer posts) it is very useful to have a better idea of when events happened relative to each other, e.g. if there's a post and multiple near-identical answers, but their display age is just "yesterday", it's useful to know how far apart the answers were posted to rule out plagiarism. If one of the near-identical answers was posted several hours after the other(s), then plagiarism can't be ruled our. If they were posted within minutes of each other (especially if this is very soon after the question itself was posted), then it's much more likely that the users just came to the same answer independently.

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Here are a few suggestions to fix this behaviour:

• Show more precision in the 1 hour <= 72 hours age range, e.g. by conflating their display format to "{x} hour(s), {y} min(s) ago" or similar.

• Always show dates/times as ISO 8601 UTC format. This might not be well-recieved, since at any given time, a very small proportion of users will be in a timezone with no UTC offset. It's possible to use getTimeZoneOffset() to fix this, so dates/times could always be shown in the local time.

• Show the time (H:mm or HH:mm) for all events that occurred this local calendar day in the local time zone, and switch to MMM dd "at" H:mm and MMM dd 'yy "at" H:mm for events that occured before this local calendar day. The precision for all posts would then be 1 minute regardless of the age.