Adding hours and minutes to current date (Only to date not to time)

Hi,
I want to add some hours and minutes to the current date. For example, if the current date is "July 16, 2012 15:20", i want to add 5 hours 30 minutes to "July 16, 2012 00:00" not to "July 16, 2012 15:20". Please help.
Thanks!