Do you know how to program? Let's assume you do. (Because if you don't, what the heck are you doing here?
)
There's nothing to "know" about doing this, really. You have a fixed background which is the clock face. You have hands that move according to what time is. The angle (call it theta) of the minute hand is related to the minutes of the hour by the formula theta = x*6, where is the x number of minutes. The hour hand theta is more complicated but let's just think through it right now. 12 hours in the unit circle = 360/12 degrees per hour, or 30°. theta = 30*h + 30*(minutes/60).
Now decide how you are going to display the hands as they tick around. You can use Flash (or possibly HTML) to display the image of a clock hand which is rotated theta degrees. 3D css transforms are only supported in the most recent browsers, but can also be used. I don't think timing the display of many many copies of the same rotated image is at all advisable.
