Date method of as.POSIXct does not respect tz

Martin Maechler 
    on Fri, 23 Sep 2022 11:04:12 +0200 writes:

Kurt Hornik 
    on Fri, 23 Sep 2022 09:57:49 +0200 writes:

Martin Maechler writes:

    > Currently in R-devel,

    R> as.POSIXlt.Date

    > function (x, ...) 
    > {
    >    if (any((y <- unclass(x)) > .Machine$integer.max, na.rm = TRUE)) 
    >         as.POSIXlt(.POSIXct(y * 86400), tz = "UTC")
    >    else .Internal(Date2POSIXlt(x))
    > }

    R> as.POSIXct.Date

    > function (x, ...) 
    > .POSIXct(unclass(x) * 86400)

    > Adding tz to the latter is easy, and the former could do the if() part
    > also with a given tz without needing to change the .Internal?

Genau!  Even more elegantly than I first thought when I wrote
"post-processing":

The following even adds internal consistency inside as.POSIXlt.Date() :

as.POSIXlt.Date <- function(x, tz = "UTC", ...) {
    as.POSIXlt(if(any((y <- unclass(x)) > .Machine$integer.max, na.rm = TRUE))
                   .POSIXct(y * 86400)
               else
                   .Internal(Date2POSIXlt(x))
             , tz = tz)
}

because now, tz is even *formally* treated the same in both
cases (whereas previously it only appeared visually in one case).

So probably, another reason to go there.
Note that I also think we'd keep the    tz = "UTZ"
default argument, even when the
other  as.POSIX[cl]t() methods have 'tz = ""'