[R] Reading a datetime vector

[D Wolf]

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
	[[alternative HTML version deleted]]