work with date and hour

Hello,  
  
  I have one  doubts simple, but I don't get to find the solution:   
  
   1 - do I have a table with following structure, in this table I do
need to work with date and hour, type a calendar to determine the
program will be executed, as I can make this selection?

    2 - as I do to select one hour >= the current hour?


        Table:

                agenda
                         (hora time,
                          data date)


..Att

Carlos