This is a good one. I have to say I've never heard this question before. 12:00 o'clock or 2:00 o'clock.....hum.
When the timing light flashes, you want it to flash when the mark, the straight line groove, on the damper is at the 1st notch on the timing mark. The timing mark is the notch on the sheet metal tab that's welded to the cam shaft cover plate. This "tab" is called the "timing plate" The timing plate has numbers on it. 0, 1, 2, 3. When the engine is at 0 degrees advance, the timing mark on the damper and the 0 notch on the timing plate will all be side by side, when the timing light flashes. There is no 12:00 oclock, 2:00 oclock. If the timing light does not flash when timing mark and 0 degree timing tab line up, then you have to move (slowly) the distributor. Ease off the tightness of the hold-down screw that's holding the distributor in place and try to rotate it...the distributor....clockwise, or counterclockwise....until the timing mark on the damper "moves" to the 0 on the timing plate...that's attached to the cam cover.
When in doubt, go buy a Haynes Automotive Repair Manual and they will walk you through the timing process. Remember to unplug the wire to the distributor BEFORE adjusting the distributor, and to replug it AFTER setting the distributor to 0 degrees. The ECM will do the timing for you.