[R] How to convert European short dates to ISO format?

[Martin Maechler]

>>>>> Rich Shepard 
>>>>>     on Thu, 11 Jun 2020 06:29:13 -0700 writes:

    > On Thu, 11 Jun 2020, Martin Maechler wrote:
    >> > Look at Hadley Wickham's 'tidyverse' collection as >
    >> described in R for Data Science. There are date,
    >> datetime, > and time functions that will do just what you
    >> want.

    >> I strongly disagree that automatic guessing of date
    >> format is a good idea:

    > Martin,

    > I think either you misunderstood what I wrote or I was not
    > sufficiently explicit in my brief response. I did not mean
    > to imply there was any automatic guessing
    > involved. Specifying input and output formats is required.

Well, ok.  Yes, then I misunderstood.  I know there *are* R
packages out there which boast automatically finding the correct format.

If you are willing to specify the input format, I don't see why
one should use the huge tidyverse  instead of just using the
potent enough base R functions,  one of which Jeff Newmiller was
talking about (and to whom you replied saying you'd rather use
the extra functions).

    > Reading Hadley's book I was impressed that one could
    > specify the format of dates in the dataset and convert
    > them all to the ISO-8601 format. Before learning this I'd
    > use emacs regex to do the reformating I needed (or,
    > sometimes, awk).

Well, as you know I use emacs even more than R (because I use R
via emacs's ESS),  but I think I wouldn't use it to transform
dates or date times [well, unless such a date/datetime column
is so severely messed up that one format is not appropriate for
at least a few large chunks of these] because I'd rather try to
use completely reproducible R code from the beginning of
cleaning/reading/analysing the raw data to the end.

And for that, base R is entirely sufficient in spite of all the
advertisements of the many date/time formatting packages.
But yes, I wrote more about this about 10 weeks ago on the
R-devel list here  (which also seemed to have been
rather mis-understood, for which I must mostly blame myself of course) :

  https://stat.ethz.ch/pipermail/r-devel/2020-April/079260.html

In that thread, the following  'R News' article was mentioned as
good introduction in the subject from a 'base R' (+ "almost
recommended" package 'chron') point of view 

  https://www.researchgate.net/publication/229087103_R_Help_Desk_Date_and_time_classes_in_R

which is really from here

  https://www.r-project.org/doc/Rnews/Rnews_2004-1.pdf

'R News' was the predecessor of the
R Journal, https://journal.r-project.org/

I think we should leave it here, because we've been diverting
too much.

Best,
Martin