how to find the index of a row a certain date in r programming code example

Example: get only the days from a timeseries in r

seq.POSIXt(from=as.POSIXlt("01-01-2016 10:00:00",format="%m-%d-%Y %H:%M:%S"),by=60*60*24, length.out = 3, format="%m-%d%-%Y %H:%M:%S", tz = "Etc/GMT+2")
# "2016-01-01 10:00:00 UTC" "2016-01-02 10:00:00 UTC" "2016-01-03 10:00:00 UTC"