A "left-handed" clock has its numbers printed counter-clockwise and runs counter-clockwise to point at them, effectively performing as a mirror image to a normal clock. Between noon and midnight, at what times are the hands of a left-handed clock pointing in exactly the same directions as those of a regular clock (comparing only hour and minute hands, which may be swapped.)
Source: Original. [You may ignore any effect due to the electromagnetic weak force.]
In order for the hands of left and right handed clocks to be in the same positions at the same time, one of two things can be true: (1) the hour hands are in the same place, and the minute hands are in the same place. This happens only at 6:00 and 12:00. (2) the hour and minute hands are swapped. This requires the hour and minute hands to form a mirror-image pair through the vertical bisector of each clock face. For case 2, at a time of A hours and B minutes past noon, the hour hand will be pointing between the A and A+1, B/60 of the way past the hour. The minute hand will be at B/5. We need A + B/60 + B/5 = 12, because one hand must be as far past the 12 as the other one needs to reach it. So A + 13B/60 = 12. For each A from 0 to 11 you can find a solution; A=12 gives the 12:00 solution already found in the first part. For A = 0, 13B/60 = 12, or B = 720/13 = 55 and 5/13, for a time of 12:55 and 5/13. For A = 1, 13B/60 = 11, or B = 660/13 = 50 and 10/13, or a time of 1:50 and 10/13. For A = 2, 13B/60= 10, B = 600/13 = 46 and 2/13, for the time 2:46 and 2/13. Likewise we get 3:41 and 7/13, 4:36 and 12/13, 5:32 and 4/13, 6:27 and 9/13, 7:23 and 1/13, 8:18 and 6/13, 9:13 and 11/13, 10:09 and 3/13, and 11:04 and 8/13.Dan Chirica listed these times digitally. In addition to 12:00 and 6:00,
0:55:23 1:50:46 2:46:9 3:41:32 4:36:55 5:32:18 6:27:41 7:23:4 8:18:27 9:13:50 10:9:13 11:4:36