Detect the Exact Time (hour and minute; hm) of Daylight Saving Time (DST) Change
Source:R/daylight_saving.R
dst_switch_hm.RdIdentifies the precise local time when a DST transition occurs on a given date in a specified time zone.
Usage
dst_switch_hm(date, tz = tz2(), interval = 1)Arguments
- date
A string in "YYYY-MM-DD" format or a Date object.
- tz
A valid time zone name (default is "America/Vancouver"), used to determine DST rules. Use
OlsonNames()to see all valid options.- interval
An integer (1–59) specifying the time resolution in minutes used to detect DST changes (default: 1, meaning 1 minute). You almost never need to change this.
Value
A POSIXct object indicating the time just before the DST transition.
If no DST change is detected on the specified date, the function returns NULL
with a warning.
Details
The function detects DST changes using differences in DST status across time
intervals during the given date. It handles "skipped" or "duplicated" times
(as occurs during spring and fall transitions) using both dst() and NA time gaps.
In the case of ambiguous or unresolvable transitions, NULL is returned with a warning.
Examples
dst_switch_hm("2020-03-08", tz = "America/Vancouver")
#> [1] "2020-03-08 01:59:00 PST"
dst_switch_hm("2020-11-01", tz = "America/Vancouver")
#> [1] "2020-11-01 00:59:00 PDT"
dst_switch_hm("2020-07-01", tz = "Etc/UTC") # No DST change
#> Warning: No DST transition detected on this date in the specified time zone.
#> NULL