When you have more LED's than output pins (as you do) you get to decide between more output pins or a matrix. For more output pins you would probably want shift registers. Four 8-bit registers would work four your design. For each output pin you will need a resistor to limit the current going to the LED. Also make sure your shift register outputs can handle the current required by your LED (typically 20 mA).
If this is to be a clock and you want to keep fairly accurate time for mare than a few hours, be sure to get either a RealTimeClock chip or a source of accurate time information (GPS or Internet access).