Interesting question! Over the years, I've been told by several people
that clocks' hands in advertisements are set at 10:10 because this was
the time of day when Abraham Lincoln was shot, or the time when he
died. This is a fascinating explanation, but there isn't a shred of
evidence for it (and, in fact, Lincoln was shot at 10:15 PM, and died
the next morning at 7:22). Exactly the same myth is sometimes reported
with John F. Kennedy or Martin Luther King as the person being
memorialized in the clock ads.

I have gathered some information on the subject for you. The consensus
of opinion (confirmed by Timex) is that clock and watch hands in
advertisements are typically set at 10:10 so that the company's logo
will be well-displayed. In addition, this position of the hands
resembles a smile.

"Q: WHEN YOU SEE AN AD WITH A CLOCK IN IT THE HANDS ARE ALWAYS
POSITIONED AT 10:10?

A: WE CALLED TIMEX FOR YOUR ANSWER AND IT SAYS THE HANDS ON A CLOCK
ARE PLACED AT TEN-TEN BECAUSE IT'S A CREATIVE STANDARD INDUSTRY.

TIMEX SAYS THE HANDS ON TIMEPIECES ARE PLACED AT TEN-TEN SO THE
COMPANY LOGO ON THE FACE WILL BE FRAMED AND NOT BLOCKED BY THE HANDS.
TIMEX SAYS THE INDUSTRY STANDARD USED TO BE EIGHT-TWENTY BUT THAT
LOOKED TOO MUCH LIKE A FROWN AND CREATED AN UNHAPPY LOOK.

TIMEX SAYS IN ITS ADS, THE CLOCK HANDS ARE PLACED AT TEN-NINE AND
THIRTY SIX SECONDS, EXACTLY."