[R] readxl, read_excel: how colon (:) is read ?

[Jeff Newmiller]

Both R and Excel assume a date is associated with every time object. In Excel, when you show a date it is an integer number of days since 1899-12-31 (due to a mistake made early in programming it). Whenever you show a time, it it merely displaying the time portion (fraction of a day) of a date/time. The date part of that value may or may not be 1899-12-31.

With this in mind, you are tilting at windmills hoping to import a "pure time" because no such thing exists in either program. You can choose to render a `POSIXct` as showing only the time portion when you convert it to character if you so choose.

On March 31, 2022 11:12:28 PM PDT, Patrick Giraudoux <patrick.giraudoux using univ-fcomte.fr> wrote:
>I have a unexpected behaviour reading times with colon from an Excel 
>file, using the package readxl.
>
>In an Excel sheet, I have a column with times in hours:minutes, e.g:
>
>Arrival_time
>13:39
>13:51
>
>When read from R with readxl::read_excel, this gives a tibble column 
>with full date by defaut being the last day of 1899. OK. Why not, I know 
>that POSIX variables are starting in 1900 after R doc (however I wonder 
>why here the defaut is one day before January 1, 1900
>
>> tmp$Arrival_time  [1] "1899-12-31 13:39:00 UTC" "1899-12-31 13:51:00 UTC"
>
>Well, this is not exactly what I want to. I do not care about the year 
>and the day... Therefore I decided to import this column as "text" 
>explicitely (in order to manage it within R then). And this is what I 
>get now:
>
>> read_excel("saisie_data_durban_rapaces_LPO.xlsx",sheet=2,col_types="text")  > tmp$Arrival_time [1] "0.56875000000000009" "0.57708333333333328"
>
>Can someone tell me what happens ?
>
>I would really appreciate to understand the trick...
>
>
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>
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-- 
Sent from my phone. Please excuse my brevity.