dst_check: Check that date and time conform to changes between Daylight...

In DEQrmichie/odeqcdr: ODEQ Continuous Data Review

Check that date and time conform to changes between Daylight Time and Standard Time.

Description

This function will evaluate if an hour was added or subtracted correctly to account for the switch from daylight time to standard time and vice versa. The check can only be used on timeseries occurring on or after the start of standard time on October 27, 1985 at 2:01 AM.

Usage

dst_check(
  df,
  mloc_col = "Monitoring.Location.ID",
  char_col = "Characteristic.Name",
  equip_col = "Equipment.ID",
  date_col = "Activity.Start.Date",
  time_col = "Activity.Start.Time",
  tz_col = "Activity.Start.End.Time.Zone",
  base_offset = NULL,
  awqms_bug = TRUE
)

Arguments

df	Data frame to be evaluated.
mloc_col	Column name in df holding the Monitoring Location ID. Default is "Monitoring.Location.ID".
char_col	Column name in df holding the Characteristic Name. Default is "Characteristic.Name".
equip_col	Column name in df holding the Equipment ID. Default is "Equipment.ID"
date_col	Column name in df holding the POSIXct date values. Default is "Activity.Start.Date"
time_col	Column name in df holding the POSIXct time values. Default is "Activity.Start.Time".
tz_col	Column name in df holding the timezone string values. Default is tz_col ="Activity.Start.End.Time.Zone".
base_offset	The numeric offset from UTC representing the "correct time". Using Pacific Standard Time the base_offset=-8. For Pacific Daylight Time the base_offset=-7. The Default is NULL and the time at the offset at the beginning of the deployment period is considered the correct time.
awqms_bug	Due to a bug in AWQMS, results with the exact same Monitoring.Location.ID, Equipment.ID, Characteristic.Name, Start.Date, Start.Time, and Result.Unit but different Time Zone values are not allowed, even if they occur during the transition from daylight time to standard time. By setting awqms_bug=TRUE (the default) one second is added to the repeat POSIXct time values that fall between 1:00 AM and 1:59 AM right after the switch to standard time. This is here as a work around until the AWQMS bug is fixed.

Details

The dst check fails and time is adjusted when either of the two conditions occur:

1. When there are results recorded between 2:00 AM and 2:59 AM when daylight savings begins. As an example, in 2020 the switch from standard time to daylight time (+1 hour) occurred on March 8, 2020 at 2:00 AM. In a time series where samples are collected every 30 minutes there should be no results recorded from 2:00 AM until 2:59 AM. If there are results recorded during this period it's likely an adjustment to daylight savings time was not made.

2. When there is only one timestamp recorded for any results between 1:00 AM and 1:59 AM after the transition back to standard time (-1 hour). As an example, in 2020 the switch from daylight savings back to standard time occurred on November 1, 2020 at 2:00 AM resulting in a repeat of time between 1:00 AM and 1:59 AM. If there are not duplicate time stamps recorded it is likely the adjustment to standard time was not made.

When one of the conditions are detected, the time at the beginning of the deployment period is considered the correct time and the appropriate UTC offset is applied for daylight savings from that point forward. Use 'base_offset' if a specific offset from UTC is desired instead. For example if the time stamp were all recorded using Pacific Standard Time the base_offset=-8. For Pacific Daylight Time the base_offset=-7. The default is to use the offset at the time of deployment, base_offset=NULL.

The dst check evaluates each deployment [Monitoring.Location.ID, Characteristic.Name, Equipment.ID] and any adjustments are made only to an individual deployment. A manual review of the results is recommend.

Daylight Savings in Oregon since 1986

1986 - 2006: Daylight savings time began by adding on hour (+1) on the first Sunday in April at 2:00 AM. Daylight savings time ended by subtracting an hour (-1) on the last Sunday in October at 2:00 AM.

2007 - Current: Daylight savings time begins by adding an hour (+1) on the second Sunday in March at 2:00 AM. Daylight savings time ends by subtracting an hour (-1) on the first Sunday in November at 2:00 AM.

Value

Vector of corrected datetime in POSISXct.

DEQrmichie/odeqcdr documentation built on Feb. 15, 2025, 10:01 a.m.