I have a date/time imported from Excel in my dataframe oooi (with
several hundred thousand rows), for example the input data near row 3100 is
ActualOnLocal
11/12/2008 21:35
11/12/2008 22:03
11/12/2008 22:12
11/12/2008 22:38
11/12/2008 23:16
11/12/2008 23:23
11/13/2008 7:00
11/13/2008 7:03
11/13/2008 7:05
11/13/2008 7:11


I want to convert the column to POSIXct
oooi$dpt <- as.POSIXct(oooi$ActualOnLocal, tz="", format="%m/%d/%Y %H:%M")
It works for the first 3099 rows. But after that all the rows come out
as NA:
> oooi$dpt
.....
[3089] "0011-12-20 EST" "0011-12-20 EST" "0011-12-20 EST" "0011-12-20 EST"
 [3093] "0011-12-20 EST" "0011-12-20 EST" "0011-12-20 EST" "0011-12-20 EST"
 [3097] "0011-12-20 EST" "0011-12-20 EST" "0011-12-20 EST" NA             
 [3101] NA               NA               NA               NA             
 [3105] NA               NA               NA               NA         
....
What can be causing this? I see nothing strange in the data in the dataframe
> oooi$ActualOnLocal[3090:3120]
 [1] 11/12/2008 20:17 11/12/2008 20:24 11/12/2008 20:36 11/12/2008 20:50
 [5] 11/12/2008 21:35 11/12/2008 22:03 11/12/2008 22:12 11/12/2008 22:38
 [9] 11/12/2008 23:16 11/12/2008 23:23 11/13/2008 7:00  11/13/2008 7:03
[13] 11/13/2008 7:05  11/13/2008 7:11  11/13/2008 7:12  11/13/2008 7:21
[17] 11/13/2008 7:23  11/13/2008 7:23  11/13/2008 7:25  11/13/2008 7:27
[21] 11/13/2008 7:30  11/13/2008 7:32  11/13/2008 7:33  11/13/2008 7:34
[25] 11/13/2008 7:34  11/13/2008 7:35  11/13/2008 7:37  11/13/2008 7:38
[29] 11/13/2008 7:39  11/13/2008 7:41  11/13/2008 7:45
94093 Levels: 1/1/2009 10:00 1/1/2009 10:01 1/1/2009 10:04 ... 9/9/2009 9:59

What is causing the conversion to suddenly fail?

Thanks,
Jim


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