Dates and Time Series

UTC Time Shift

Fixed Instants

POSIXct stores date-time instants. Using an explicit UTC time zone keeps examples deterministic across machines.

Program

Play the script to shift a fixed UTC instant by selected hours.

hour_shift
utc_time_shift.R
Replay: real traced execution (multi-file project)
base_time <- as.POSIXct("2026-01-01 08:00:00", tz = "UTC")
hour_shift <- 0
event_time <- base_time + hour_shift * 3600
stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")
label <- paste("UTC", stamp)
cat(label, "\n", sep = "")

base_time <- as.POSIXct("2026-01-01 08:00:00", tz = "UTC")
hour_shift <- 6
event_time <- base_time + hour_shift * 3600
stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")
label <- paste("UTC", stamp)
cat(label, "\n", sep = "")

base_time <- as.POSIXct("2026-01-01 08:00:00", tz = "UTC")
hour_shift <- 12
event_time <- base_time + hour_shift * 3600
stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")
label <- paste("UTC", stamp)
cat(label, "\n", sep = "")

  1. base_time ← 2026-01-01 08:00 UTC

    1base_time <- as.POSIXct("2026-01-01 08:00:00", tz = "UTC")2hour_shift <- 0
    values this step2026-01-01 08:00 UTCbase_time

  2. hour_shift ← 0

    1base_time <- as.POSIXct("2026-01-01 08:00:00", tz = "UTC")2hour_shift <- 03event_time <- base_time + hour_shift * 3600
    values this step0hour_shift

  3. event_time ← 2026-01-01 08:00 UTC

    2hour_shift <- 03event_time <- base_time + hour_shift * 36004stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")
    values this step2026-01-01 08:00 UTCevent_time2026-01-01 08:00 UTCbase_time0hour_shift

  4. stamp ← 2026-01-01 08:00

    3event_time <- base_time + hour_shift * 36004stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")5label <- paste("UTC", stamp)
    values this step2026-01-01 08:00stamp2026-01-01 08:00 UTCevent_time

  5. label ← UTC 2026-01-01 08:00

    4stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")5label <- paste("UTC", stamp)6cat(label, "\n", sep = "")
    values this stepUTC 2026-01-01 08:00label2026-01-01 08:00stamp

  6. cat(label, " ", sep = "")

    5label <- paste("UTC", stamp)6cat(label, "\n", sep = "")
    outputUTC 2026-01-01 08:00
    values this stepUTC 2026-01-01 08:00label

  1. base_time ← 2026-01-01 08:00 UTC

    1base_time <- as.POSIXct("2026-01-01 08:00:00", tz = "UTC")2hour_shift <- 6
    values this step2026-01-01 08:00 UTCbase_time

  2. hour_shift ← 6

    1base_time <- as.POSIXct("2026-01-01 08:00:00", tz = "UTC")2hour_shift <- 63event_time <- base_time + hour_shift * 3600
    values this step6hour_shift

  3. event_time ← 2026-01-01 14:00 UTC

    2hour_shift <- 63event_time <- base_time + hour_shift * 36004stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")
    values this step2026-01-01 14:00 UTCevent_time2026-01-01 08:00 UTCbase_time6hour_shift

  4. stamp ← 2026-01-01 14:00

    3event_time <- base_time + hour_shift * 36004stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")5label <- paste("UTC", stamp)
    values this step2026-01-01 14:00stamp2026-01-01 14:00 UTCevent_time

  5. label ← UTC 2026-01-01 14:00

    4stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")5label <- paste("UTC", stamp)6cat(label, "\n", sep = "")
    values this stepUTC 2026-01-01 14:00label2026-01-01 14:00stamp

  6. cat(label, " ", sep = "")

    5label <- paste("UTC", stamp)6cat(label, "\n", sep = "")
    outputUTC 2026-01-01 14:00
    values this stepUTC 2026-01-01 14:00label

  1. base_time ← 2026-01-01 08:00 UTC

    1base_time <- as.POSIXct("2026-01-01 08:00:00", tz = "UTC")2hour_shift <- 12
    values this step2026-01-01 08:00 UTCbase_time

  2. hour_shift ← 12

    1base_time <- as.POSIXct("2026-01-01 08:00:00", tz = "UTC")2hour_shift <- 123event_time <- base_time + hour_shift * 3600
    values this step12hour_shift

  3. event_time ← 2026-01-01 20:00 UTC

    2hour_shift <- 123event_time <- base_time + hour_shift * 36004stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")
    values this step2026-01-01 20:00 UTCevent_time2026-01-01 08:00 UTCbase_time12hour_shift

  4. stamp ← 2026-01-01 20:00

    3event_time <- base_time + hour_shift * 36004stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")5label <- paste("UTC", stamp)
    values this step2026-01-01 20:00stamp2026-01-01 20:00 UTCevent_time

  5. label ← UTC 2026-01-01 20:00

    4stamp <- format(event_time, "%Y-%m-%d %H:%M", tz = "UTC")5label <- paste("UTC", stamp)6cat(label, "\n", sep = "")
    values this stepUTC 2026-01-01 20:00label2026-01-01 20:00stamp

  6. cat(label, " ", sep = "")

    5label <- paste("UTC", stamp)6cat(label, "\n", sep = "")
    outputUTC 2026-01-01 20:00
    values this stepUTC 2026-01-01 20:00label
POSIXct `as.POSIXct(..., tz = "UTC")` creates a date-time instant with an explicit zone.
seconds `hour_shift * 3600` converts hours into seconds for time arithmetic.
UTC Formatting with `tz = "UTC"` avoids host-local time-zone differences.