[R] Reading a datetime vector

Jim Lemon drjimlemon at gmail.com
Fri Feb 19 07:32:50 CET 2016

Hi Doug,
For one thing, you may be using the wrong format. Your example format has
no seconds field. The other thing to watch is whether the data are in
%m/%d/%Y or %d/%m/%Y date format. If the latter, you would probably get
that error on dates like 19/02/2016.


On Fri, Feb 19, 2016 at 8:12 AM, D Wolf via R-help <r-help at r-project.org>

> Hello,I am trying to read a data frame column named DateTimeStamp. The
> time is in GMT in this format: 1/4/2013 23:30
> require(xlsx)
> df2_TZ = read.xlsx2("DF_exp.xlsx", sheetName = "Sheet1")
> It's good to that line. But these three lines, which makes the dataframe,
> converts the column's values to NA:df2_TZ$DateTimeStamp =
> as.POSIXct(df2_TZ$DateTimeStamp, format="%m/%d/%Y %H:%M:%S", tz="GMT")
> and... df2_TZ$DateTimeStamp =
> as.POSIXct(as.character(df2_TZ$DateTimeStamp), format = "%m/%d/%Y %H:%M:%S")
> and...df2_TZ$DateTimeStamp = as.Date(df2_TZ$DateTimeStamp, format =
> "%m/%d/%Y %H:%M:%S")
> This line returns and error...df2_TZ$DateTimeStamp =
> as.POSIXct(as.Date(df2_TZ$DateTimeStamp), format = "%m/%d/%Y %H:%M:%S")
> "Error in charToDate(x) :   character string is not in a standard
> unambiguous format"
> Additionally, I need to convert from GMT to North American time zones, and
> I think the advice on this page would be good for that:
> http://blog.revolutionanalytics.com/2009/06/converting-time-zones.html
> My ultimate goal is to write an R program that finds data in another
> variable in df2_TZ that corresponds to a date and time that match up with
> the date and time in another data frame. For now, any help reading the
> column would be much appreciated.
> Thank You,Doug
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