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  • date_zone() gets the time zone.

  • date_set_zone() sets the time zone. This retains the underlying duration, but changes the printed time depending on the zone that is chosen.

Usage

date_zone(x)

date_set_zone(x, zone)

Arguments

x

[POSIXct / POSIXlt]

A date-time vector.

zone

[character(1)]

A valid time zone to switch to.

Value

  • date_zone() returns a string containing the time zone.

  • date_set_zone() returns x with 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 <- as.Date("2019-01-01")
try(date_zone(x))
#> Error in date_zone(x) : Can't get the zone of a 'Date'.
try(date_set_zone(x, "America/New_York"))
#> Error in date_set_zone(x, "America/New_York") : 
#>   Can't set the zone of a 'Date'.

x <- as.POSIXct("2019-01-02 01:30:00", tz = "America/New_York")
x
#> [1] "2019-01-02 01:30:00 EST"

date_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_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.POSIXct()`!
x %>%
  as_naive_time() %>%
  as.POSIXct("America/Los_Angeles")
#> [1] "2019-01-02 01:30:00 PST"

y <- as.POSIXct("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
#> <time_point<naive><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.POSIXct(y_nt, "Europe/Helsinki"))
#> Error in stop_clock(message, "clock_error_nonexistent_time") : 
#>   Nonexistent time due to daylight saving time at location 1.
#>  Resolve nonexistent time issues by specifying the `nonexistent` argument.

as.POSIXct(y_nt, "Europe/Helsinki", nonexistent = "roll-forward")
#> [1] "2021-03-28 04:00:00 EEST"
as.POSIXct(y_nt, "Europe/Helsinki", nonexistent = "roll-backward")
#> [1] "2021-03-28 02:59:59 EET"