Re: Bring back VMS Standard Date/Time...
If the ISO standard is being followed anyone who mis-interprets it has only themselves to blame. The significance of ISO dates is that (a) they collate properly and (b) they are natural language independent.
If I'm writing up genealogical or historical stuff I do, in fact, use something like 15 Sep 2020. It doesn't have to be collated and the whole text is in English so language dependency of the data is a minor issue.
Dates as data are an entirely different kettle of snakes.
My database engine of choice is Informix which, internally, stores dates numerically where 1 is the first day of the last year of the 19th century (nobody explained it to them) and you can have that converted in a large number of ways depending on language settings and an environment variable. Spreadsheets should work in similar ways and switch representation on demand.
But get into historical dates and if you're lucky all you have to worry about are Julian/Gregorian changeovers and hope that the first part of the year it was written out unambiguously, e.g. 1731/2*.
If you're unlucky you end up with something like: "Friday before the Feast of the Apostles Philip and James in the fifth year of the reign of King Edward" or even worse "the Friday in Pentecost, in the year abovesaid" and hope that some kind editor has done the hard work of translating it all. And if you're really unlucky you find that the kind editor hadn't noticed that a whole year's records were missing so all the dates were mistranslated**.
* I came across the work of an antiquarian who avoided that - I suspect as a deliberate choice - so he recorded a will dated and proved (i.e. testator died between the dates) apparently several months before he was being sent instructions for his part in the latest episode of the Hundred Years War.
** Several hours with an Easter calculator, Googling of saints' days and cal to sort it out.