[Rd] Non-deterministic POSIXlt tzone in Europe/London around UTC 0

[Michael Chirico]

As a test case I have code running 'as.POSIXlt(1:10)', which can
unfortunately produce non-deterministic results:

TZ=Europe/London R
attr(as.POSIXlt(as.numeric(1:10)), 'tzone')
# [1] "Europe/London" "GMT"           "BST"
attr(as.POSIXlt(as.numeric(1:10)), 'tzone')
# [1] "Europe/London" "BST"           "BST"

Is this intended behavior? I don't see this possibility described in
any of ?DateTimeClasses, ?strptime, ?timezones, or ?as.POSIXlt. Some
caching is mentioned around .sys.timezone, but the above snippets
don't have any relationship that I can see.

Mike C