What are the standard unambiguous date formats for string-to-date conversion in R

Question

Please consider the following    R --vanilla   gt  as Date  01 Jan 2000   Error in charToDate x        character string is not in a standard unambiguous format   But that date clearly is in a standard unambiguous format  Why the error message   Worse  an ambiguous date is apparently accepted without warning or error and then read incorrectly    gt  as Date  01 01 2000    1   0001-01-20    I ve searched and found 28 other questions in the  R  tag containing this error message  All with solutions and workarounds involving specifying the format  iiuc  This question is different in that I m asking where are the standard unambiguous formats defined anyway  and can they be changed   Does everyone get these messages or is it just me  Perhaps it is locale related   In other words  is there a better solution than needing to specify the format   29 questions containing   R  standard unambiguous format    gt  sessionInfo   R version 2 15 2  2012-10-26  Platform  x86 64-w64-mingw32 x64  64-bit   locale   1  LC COLLATE English United Kingdom 1252  2  LC CTYPE English United Kingdom 1252  3  LC MONETARY English United Kingdom 1252  4  LC NUMERIC C  5  LC TIME English United Kingdom 1252  attached base packages   1  stats     graphics  grDevices utils     datasets  methods   base

User · Answer

This works perfectly for me  not matter how the date was coded previously   library lubridate  data created date1  lt - mdy hm data created at  data created date1  lt - as Date data created date1

User · Answer

As a complement to  JoshuaUlrich answer  here is the definition of function as Date character   as Date character function  x  format                   charToDate  lt - function x            xx  lt - x 1L          if  is na xx                 j  lt - 1L             while  is na xx   amp  amp   j  lt - j   1L   lt   length x   xx  lt - x j              if  is na xx                    f  lt -   Y- m- d                    if  is na xx      is na strptime xx  f  lt -   Y- m- d                tz    GMT        is na strptime xx  f  lt -   Y  m  d                tz    GMT                  return strptime x  f           stop  character string is not in a standard unambiguous format             res  lt - if  missing format            charToDate x      else strptime x  format  tz    GMT       as Date res     lt bytecode  0x265b0ec gt   lt environment  namespace base gt    So basically if both strptime x  format   Y- m- d   and strptime x  format   Y  m  d   throws an NA it is considered ambiguous and if not unambiguous

User · Answer

Converting the date without specifying the current format can bring this error to you easily   Here is an example   sdate  lt -  2015 10 10    Convert without specifying the Format   date  lt - as Date sdate4       gt  This will generate the same error   Error in charToDate x   character string is not in a standard unambiguous format       Convert with specified Format   date  lt - as Date sdate4  format     Y  m  d        gt  Error Free Date Conversion

User · Answer

In other words  is there a better solution than needing to specify the format    Yes  there is now  ie in late 2016   thanks to anytime  anydate from the anytime package    See the following for some examples from above   R gt  anydate c  01 Jan 2000    01 01 2000    2015 10 10     1   2000-01-01   2000-01-01   2015-10-10  R gt     As you said  these are in fact unambiguous and should just work  And via anydate   they do   Without a format

User · Answer

This is documented behavior   From  as Date      format  A character string   If not specified  it will try                Y- m- d   then    Y  m  d   on the first non- NA  element              and give an error if neither works    as Date  01 Jan 2000   yields an error because the format isn t one of the two listed above    as Date  01 01 2000   yields an incorrect answer because the date isn t in one of the two formats listed above   I take  standard unambiguous  to mean  ISO-8601   even though as Date isn t that strict  as   m  d  Y  isn t ISO-8601    If you receive this error  the solution is to specify the format your date  or datetimes  are in  using the formats described in  strptime  Be sure to use particular care if your data contain day month names and or abbreviations  as the conversion will depend on your locale  see the examples in  strptime and read  LC TIME

[r] What are the "standard unambiguous date" formats for string-to-date conversion in R?

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