Hmm maybe not the most creative of all ideas but how about converting the date to a string variable? If you later want to use it in KNIME you might have to convert it back. Another thing could be to extract the UNIX timestamp from the date variable.
If you open the R Snippet and you evaluate the results you could insert something like head(knime.in) to see how your manipulations go and indeed R is displaying the date variables as you would expect.
knime.in$date2 <- as.POSIXct(strptime(knime.in$date1, “%Y-%m-%d”), tz=‘Europe/Berlin’)
knime.in$date3 <- as.character(knime.in$date2)
kn_example_r_date.knwf (28.3 KB)