Use geographical region for timezones

Fixes:

── Error ('test-timezone.R:7:5'): with_timezone: changes the time zone ─────────
Error in `format.POSIXlt(as.POSIXlt(x, tz), format, usetz, ...)`: output string exceeded 2048 bytes
Backtrace:
▆
1. ├─testthat::expect_true(...) at test-timezone.R:7:4
2. │ └─testthat::quasi_label(enquo(object), label, arg = "object")
3. │ └─rlang::eval_bare(expr, quo_get_env(quo))
4. ├─... %in% c("PDT", "PST")
5. ├─withr::with_timezone("US/Pacific", format(Sys.time(), "%Z"))
6. │ └─withr::with_envvar(c(TZ = tz), code)
7. │ └─base::force(code)
8. ├─base::format(Sys.time(), "%Z")
9. └─base::format.POSIXct(Sys.time(), "%Z")
10. ├─base::structure(...)
11. └─base::format.POSIXlt(as.POSIXlt(x, tz), format, usetz, ...)

Notes from Kurt:

The errors for r-devel-linux-x86_64-debian-gcc (which will eventually
also show for the other Debian-based checks) are from a recent system
upgrade of the tzdata package which dropped the legacy timezone
symlinks that are not following the current rule of using the
geographical region
(continent or ocean) and city name (the "backward" links from tzdata),
such as

  GB            -> Europe/London
  NZ            -> Pacific/Auckland
  US/Eastern    -> America/New_York
  US/Pacific    -> America/Los_Angeles

R/timezone.R

@@ -17,7 +17,7 @@
 #' @examples
 #' Sys.time()
 #' with_timezone("Europe/Paris", print(Sys.time()))
-#' with_timezone("US/Pacific", print(Sys.time()))
+#' with_timezone("America/Los_Angeles", print(Sys.time()))
 #'
 with_timezone <- function(tz, code) {
   reset_timezone()
@@ -34,7 +34,7 @@ with_timezone <- function(tz, code) {
 #' }
 #'
 #' fun2 <- function() {
-#'   local_timezone("US/Pacific")
+#'   local_timezone("America/Los_Angeles")
 #'   print(Sys.time())
 #' }
 #' Sys.time()

tests/testthat/test-timezone.R

@@ -5,7 +5,7 @@ describe("with_timezone", {
     expect_true(
       with_timezone("CET", format(Sys.time(), "%Z")) %in% c("CET", "CEST"))
     expect_true(
-      with_timezone("US/Pacific", format(Sys.time(), "%Z")) %in% c("PDT", "PST"))
+      with_timezone("America/Los_Angeles", format(Sys.time(), "%Z")) %in% c("PDT", "PST"))
 
   })
 
@@ -15,7 +15,7 @@ describe("with_timezone", {
     expect_identical(cur, Sys.timezone())
 
     cur <- Sys.timezone()
-    expect_equal(with_timezone("US/Pacific", Sys.timezone()), "US/Pacific")
+    expect_equal(with_timezone("America/Los_Angeles", Sys.timezone()), "America/Los_Angeles")
     expect_identical(cur, Sys.timezone())
   })
 })
@@ -30,8 +30,8 @@ describe("local_timezone", {
       with_timezone("CET", Sys.timezone()),
       fun("CET"))
     expect_identical(
-      with_timezone("US/Pacific", Sys.timezone()),
-      fun("US/Pacific"))
+      with_timezone("America/Los_Angeles", Sys.timezone()),
+      fun("America/Los_Angeles"))
   })
 
   it("restores the time zone", {
@@ -42,7 +42,7 @@ describe("local_timezone", {
     }
     fun("CET")
     expect_identical(cur, Sys.timezone())
-    fun("US/Pacific")
+    fun("America/Los_Angeles")
     expect_identical(cur, Sys.timezone())
   })
 })