I have a data frame which is similar to `dd` where 

```
dd = data.frame(date = as.Date(c("2014-04-29", "2014-04-29","2014-04-29", "2014-04-29", "2014-04-29", "2014-04-29"), format ="%Y-%m-%d"), hh = 1:6, mm = seq(0, 50, 10))

```

I want to create new variables, call them `time1` and `time2`, where

* `time1` is time of day, irregardless of the date, e.g.: in row 1 `time1 = 01:00` [hh:mm] no entry for seconds
* `time2` is `date + time1`; e.g. for row 1 `time2 = 2014-04-29 : 01:00`

Any suggestion is appreciated!