Finding first and last occurances whats the best way?

Hi everyone, I'm new here so please bear with me if I've not given you all the details you need!!

I have a spreadsheet of data which I need to manipulate. I need to find the first and last entries for a date but I can't work out how best to do it I've provided an example below, have you any suggestions?
Column A: Date Format YYYY-MM-DD HH:MM
Row 1: 03/01/2012 09:13
Row 2: 03/01/2012 09:13
Row 3: 03/01/2012 09:13
Row 4: 03/01/2012 16:47
Row 5: 03/01/2012 16:59
Row 6: 12/01/2012 09:14
Row 7: 12/01/2012 09:14
Row 8: 12/01/2012 09:14
Row 9: 12/01/2012 17:04
Row 10: 12/01/2012 17:04
Row 11: 12/01/2012 17:42

etc etc...