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Adjust Time Stamp for Daylight Saving Time (DST) Transitions in North America

Source: R/daylight_saving.R
daylight_saving_adjust.Rd

Please note this function's logic currently is based onNorth America only. This function adjusts a dataframe of visit events (e.g., feed or water visits) based on DST changes. It detects whether the current date is a DST transition day (in spring or fall), or the day after the spring DST change, and applies the appropriate time correction logic. The adjustment logic for each case is as follows:

Usage

daylight_saving_adjust(
  data_frame,
  date,
  start_col = start_col2(),
  end_col = end_col2(),
  dst_df,
  daylight_change_duration = 60,
  tz = tz2()
)

Arguments

data_frame

A data frame with two columns representing the start and end time of each visit, formatted as "HH:MM:SS".

date

A string in "YYYY-MM-DD" format or a Date object.

start_col

Name of the column recording the start time of an event (quoted), e.g.: start_col = "start"

end_col

Name of the column recording the end time of an event (quoted). e.g.: end_col = "end"

dst_df

A data frame created by get_dst_switch_info, containing DST change dates and times for each year.

daylight_change_duration

How many minutes does the clock jump or fall back on the day of daylight saving change? This should be an integer for the duration in minutes (default = 60).

tz

A valid time zone name (default is "America/Vancouver"), used to determine DST rules. Use OlsonNames() to see all valid options.

Value

A data frame adjusted for daylight saving time, or the original data if no adjustment applies.

Details

Fall DST Change Day (e.g., 1st Sunday of November):

  • North American clocks fall back from 2:00 AM to 1:00 AM, repeating the hour from 1:00 to 2:00 AM.

  • Some sensors do not repeat the 1–2 AM hour but instead continue recording 2–3 AM as if time never changed.

  • This function:

    • Removes visits that occur in the ambiguous hour (2:00 AM–3:00 AM, as recorded).

    • Shifts all visits after 3:00 AM back by 1 hour to align with the post-fallback clock time.

Spring DST Change Day (e.g., 2nd Sunday of March):

  • North American clocks in the spring will jump forward from 2:00 AM to 3:00 AM, skipping the hour between 2–3 AM.

  • Some sensors continue recording local time, resulting in inconsistent timestamps.

  • This function:

    • Removes visits that start before the DST jump (2:00 AM) and end during the skipped hour (2:00–3:00 AM).

    • Shifts all visits that occur after 2:00 AM forward by 1 hour to align with the new clock time.

Day After Spring DST Change:

  • On the day after spring DST change, sensors may still include late-night entries from the previous (DST) day, due to time "over-spill"

  • This function:

    • Identifies the first time point where time resets, based on the start time column.

    • Removes all rows all entries from the previous day if there is data spillover due to DST change.

Examples

dst_info <- get_dst_switch_info(years = 2021, tz = "America/Vancouver")
df <- data.frame(
  Start = c("01:30:00", "02:30:00", "04:00:00"),
  End = c("02:00:00", "03:00:00", "04:30:00")
)
print(df)
#>      Start      End
#> 1 01:30:00 02:00:00
#> 2 02:30:00 03:00:00
#> 3 04:00:00 04:30:00
daylight_saving_adjust(df,
  date = "2021-11-07",
  start_col = "Start",
  end_col = "End",
  dst_df = dst_info,
  tz = "America/Vancouver"
)
#>      Start       End
#> 1 3H 0M 0S 3H 30M 0S