R 4.6.2
OS X
Colleagues,
I am having a problem with conversion of a numeric to date format. In the
example shown below, the first column is the original date value.
The second column is the conversion to numeric.
In the third column, I add 0.5 to the second column.
The fourth column converts the third column back to a date format using the
following code:
FORMAT <- "%d-%b-%Y %H:%M"
SECPERDAY <- 24 * 60 * 60
SUBSUB <- structure(list(PKDOSDTC_PM_RAW = c("06-Apr-2025 10:30", "10-Dec-2025
07:15", "11-May-2025 07:30", "16-Mar-2025 08:00", "11-May-2025 08:00",
"16-Mar-2025 08:00", "22-Sep-2024 09:00", "11-Aug-2025 09:00", "20-Oct-2024
08:00", "14-Jan-2026 10:00", "03-Nov-2025 08:00"
), PM.ELAPSED = c(20184.438, 20432.302, 20219.312, 20163.333, 20219.333,
20163.333, 19988.375, 20311.375, 20016.333, 20467.417, 20395.333),
FIX.PM.ELAPSED = c(20184.938, 20432.802, 20219.812, 20163.833, 20219.833,
20163.833, 19988.875, 20311.875, 20016.833, 20467.917, 20395.833), FIX.PM.RAW
= c("06-Apr-2025 15:30", "10-Dec-2025 11:15", "11-May-2025 12:30",
"16-Mar-2025 13:00", "11-May-2025 13:00", "16-Mar-2025 13:00", "22-Sep-2024
14:00", "11-Aug-2025 14:00", "20-Oct-2024 13:00", "14-Jan-2026 14:00",
"03-Nov-2025 12:00"
)), row.names = c(36L, 71L, 120L, 183L, 253L, 288L, 316L, 400L, 414L, 505L,
519L), class = "data.frame")
SUBSUB$REVISED <- format.Date(SUBSUB$nREVISED * SECPERDAY,
format=FORMAT)
Note the following:
1. nREVISED is 0.5 larger than nORIGINAL, i.e., 12 hours
2. the difference between REVISED and ORIGINAL is either 4 or 5 hours
-- I intended it to be 12 hours.
The discrepancy of 8 or 7 hours (12 - [4 or 5]) suggests to me that the problem
involves time times; the occurrence of 4 vs. 5 is presumably due to daylight
savings time (PST vs. PDT).
I suspect that the problem can be solved by adding TZ to the code and possibly
origin. But various attempts to do this all fail.
Any suggestions?
Dennis
Dennis Fisher MD
P < (The "P Less Than" Company)
Phone: 415 307-4791
www.PLessThan.com
ORIGINAL nORIGINAL nREVISED REVISED
36 06-Apr-2025 10:30 20184.44 20184.94 06-Apr-2025 15:30
71 10-Dec-2025 07:15 20432.30 20432.80 10-Dec-2025 11:15
120 11-May-2025 07:30 20219.31 20219.81 11-May-2025 12:30
183 16-Mar-2025 08:00 20163.33 20163.83 16-Mar-2025 13:00
253 11-May-2025 08:00 20219.33 20219.83 11-May-2025 13:00
288 16-Mar-2025 08:00 20163.33 20163.83 16-Mar-2025 13:00
316 22-Sep-2024 09:00 19988.38 19988.88 22-Sep-2024 14:00
400 11-Aug-2025 09:00 20311.38 20311.88 11-Aug-2025 14:00
414 20-Oct-2024 08:00 20016.33 20016.83 20-Oct-2024 13:00
505 14-Jan-2026 10:00 20467.42 20467.92 14-Jan-2026 14:00
519 03-Nov-2025 08:00 20395.33 20395.83 03-Nov-2025 12:00
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