RODBC sqlQuery as.is returning bad results

I'm trying to import an excel worksheet into R. I want to retrieve a (character) ID column and a couple of date columns from the worksheet. The following code works fine but brings one column in as a date and not another. I think it has something to do with more leading columns being empty in the second date field.

dateFile <- odbcConnectExcel2007(xcelFile)
query <- "SELECT ANIMALID, ST_DATE_TIME, END_DATE_TIME FROM [KNWR_CL$]"
idsAndDates <- sqlQuery(dateFile,query)

So my plan now is to bring in the date columns as character fields and convert them myself using as.POSIXct. However, the following code produces only a single row in idsAndDates.

dateFile <- odbcConnectExcel2007(xcelFile)
query <- "SELECT ANIMALID, ST_DATE_TIME, END开发者_如何学运维_DATE_TIME FROM [KNWR_CL$]"
idsAndDates <- sqlQuery(dateFile,query,as.is=TRUE,TRUE,TRUE)

What am I doing wrong?

I had to move on and ended up using the gdata library (which worked). I'd still be interested in an answer for this though.