Re: Converting numerics to date format

Perhaps something like this?

as.POSIXct(SUBSUB$PKDOSDTC_PM_RAW, format =3D "%d-%b-%Y %H:%M") + 12 * 60 *=
 60

On Wed, Jun 10, 2026 at 3:24=E2=80=AFPM Dennis Fisher <[email protected]=
> wrote:
>
> R 4.6.2
> OS X
>
> Colleagues,
>
> I am having a problem with conversion of a numeric to date format.  In th=
e 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 t=
he following code:
> FORMAT                          <- "%d-%b-%Y %H:%M"
> SECPERDAY                       <- 24 * 60 * 60
> SUBSUB <- structure(list(PKDOSDTC_PM_RAW =3D c("06-Apr-2025 10:30", "10-D=
ec-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-O=
ct-2024 08:00", "14-Jan-2026 10:00", "03-Nov-2025 08:00"
> ), PM.ELAPSED =3D c(20184.438, 20432.302, 20219.312, 20163.333,  20219.33=
3, 20163.333, 19988.375, 20311.375, 20016.333, 20467.417,  20395.333), FIX.=
PM.ELAPSED =3D c(20184.938, 20432.802, 20219.812,  20163.833, 20219.833, 20=
163.833, 19988.875, 20311.875, 20016.833,  20467.917, 20395.833), FIX.PM.RA=
W =3D 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 1=
4:00", "11-Aug-2025 14:00",  "20-Oct-2024 13:00", "14-Jan-2026 14:00", "03-=
Nov-2025 12:00"
> )), row.names =3D c(36L, 71L, 120L, 183L, 253L, 288L, 316L, 400L,  414L, =
505L, 519L), class =3D "data.frame")
> SUBSUB$REVISED                  <- format.Date(SUBSUB$nREVISED * SECPERDA=
Y, format=3DFORMAT)
>
> 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 p=
roblem 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 pos=
sibly 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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