Inserting missing Date/time data

Hi everybody

I have got an hourly meteorological data for 10 years. The problem is that some of the data entries are missing. e.g.

23-April-2006 19:00
23-April-2006 20:00
23-April-2006 22:00
23-April-2006 23:00

I need to insert the rows for missing hours. Rest of the columns in the inserted row are needed to be blank. e.g.

23-April-2006 19:00
23-April-2006 20:00
23-April-2006 21:00
23-April-2006 22:00
23-April-2006 23:00

Please also note that for some years, the data entries are for half past hours. e.g.

31-Dec-2001 23:30
01-Jan-2002 00:30
01-Jan-2002 01:30
01-Jan-2002 02:30

Peace
Muhammad Zeeshan