“Why shouldn’t you tell secrets when a clock is around?”/“Because time will tell.”

A clock riddle is:
 
Q: Why shouldn’t you tell secrets when a clock is around?
A: Because time will tell.
 
The joke has been cited in print since at least 1976.
 
           
Google Books
Biggest Riddle Book in the World
By Joseph Rosenbloom
Illustrations by Joyce Behr
New York, NY: Sterling Publishing Company, Inc.
1976
Pg. 98:
Why shouldn’t you tell secrets when a clock is around?
Because time will tell.
 
21 February 1998, Seattle (WA) Times, “Safe Places—Two kids find fun, friends and safety in local after-school programs” by Kim Haub, pg. D8:
Q: Why can’t you tell secrets with a clock in the room?
A: Because time will tell.
 
Google Groups: alt.humor.puns
Puns of the Weak 06-27-03
Stan Kegel
6/27/03
(...)
Why shouldn’t you tell secrets when a clock is around?
Because time will tell. Kid’s Jokes)
 
Google Books
Penguin Pocket Jokes
By David Pickering
London, UK: Penguin Books
2006
Pg. ?;
Why can’t clocks keep secrets?
Because time will tell.
   
Twitter
marisa asbury.‏
@risarambo
why shouldnt you tell your secrets to the clock?
because time will tell!
2:53 PM - 9 Mar 2009
   
Google Books
Sensible Nonsense.. Frank’s Comic Pack:
Humour Pack Series
By Frank Paul
BookBaby
2014
Pg. ?:
Why shouldn’t you tell secrets when a clock is around?Because time will tell.
 
Twitter
Lucky Score‏
@LuckyScoreNet
Why shouldn’t you tell secrets when a clock is
around?
Because time will tell.
#Joke from #TimeJokes in #Jokes,  #Humor and #Satire
9:37 PM - 8 Sep 2017