Convert character month name to date time object

I must be missing something simple.

I have a data.frame of various date formats and I'm using lubridate which works great with everything except month names by themselves. I can't get the month names to convert to date time objects.

> head(dates)
    From         To
1       June     August
2    January   December
3 05/01/2013 10/30/2013
4       July   November
5 06/17/2013 10/14/2013
6 05/04/2013 11/23/2013

Trying to change June into date time object:

> as_date(dates[1,1])
Error in charToDate(x) : 
  character string is not in a standard unambiguous format

> as_date("June")
Error in charToDate(x) : 
  character string is not in a standard unambiguous format

• The actual year and day do not matter. I only need the month. zx8754 suggested using dummy day and year.