date_time_zone()gets the time zone.date_time_set_zone()sets the time zone. This retains the underlying duration, but changes the printed time depending on the zone that is chosen.
Arguments
- x
[POSIXct / POSIXlt]A date-time vector.
- zone
[character(1)]A valid time zone to switch to.
Value
date_time_zone()returns a string containing the time zone.date_time_set_zone()returnsxwith an altered printed time. The underlying duration is not changed.
Details
This function is only valid for date-times, as clock treats R's Date class as a naive type, which always has a yet-to-be-specified time zone.
Examples
library(magrittr)
# Cannot set or get the zone of Date.
# clock assumes that Dates are naive types, like naive-time.
x <- date_parse("2019-01-01")
try(date_time_zone(x))
#> Error in date_time_zone(x) : `x` can't be a <Date>.
#> ℹ <Date> is considered a naive time with an unspecified time zone.
#> ℹ Time zones can only be get or set for date-times (<POSIXct> or
#> <POSIXlt>).
try(date_time_set_zone(x, "America/New_York"))
#> Error in date_time_set_zone(x, "America/New_York") :
#> `x` can't be a <Date>.
#> ℹ <Date> is considered a naive time with an unspecified time zone.
#> ℹ Time zones can only be get or set for date-times (<POSIXct> or
#> <POSIXlt>).
x <- date_time_parse("2019-01-02 01:30:00", "America/New_York")
x
#> [1] "2019-01-02 01:30:00 EST"
date_time_zone(x)
#> [1] "America/New_York"
# If it is 1:30am in New York, what time is it in Los Angeles?
# Same underlying duration, new printed time
date_time_set_zone(x, "America/Los_Angeles")
#> [1] "2019-01-01 22:30:00 PST"
# If you want to retain the printed time, but change the underlying duration,
# convert to a naive-time to drop the time zone, then convert back to a
# date-time. Be aware that this requires that you handle daylight saving time
# irregularities with the `nonexistent` and `ambiguous` arguments to
# `as_date_time()`!
x %>%
as_naive_time() %>%
as_date_time("America/Los_Angeles")
#> [1] "2019-01-02 01:30:00 PST"
y <- date_time_parse("2021-03-28 03:30:00", "America/New_York")
y
#> [1] "2021-03-28 03:30:00 EDT"
y_nt <- as_naive_time(y)
y_nt
#> <naive_time<second>[1]>
#> [1] "2021-03-28T03:30:00"
# Helsinki had a daylight saving time gap where they jumped from
# 02:59:59 -> 04:00:00
try(as_date_time(y_nt, "Europe/Helsinki"))
#> Error in as_zoned_time(x, zone = tz, nonexistent = nonexistent, ambiguous = ambiguous) :
#> Nonexistent time due to daylight saving time at location 1.
#> ℹ Resolve nonexistent time issues by specifying the `nonexistent` argument.
as_date_time(y_nt, "Europe/Helsinki", nonexistent = "roll-forward")
#> [1] "2021-03-28 04:00:00 EEST"
as_date_time(y_nt, "Europe/Helsinki", nonexistent = "roll-backward")
#> [1] "2021-03-28 02:59:59 EET"