The San Diego (CA) Union originated in September 1930 what would become a popular business proverb:
 
“Confusion.—Retail jewelers assert that every man should carry two watches. But a man with one watch knows what time it is, and a man with two watches could never be sure.”
 
The saying means that receiving too much often conflicting information can make a decision more difficult to make, not easier. In 1961, Earl Wilson’s syndicated New York newspaper column credited the saying to Lee Segall of KIXL in Dallas, Texas, but Segall simply used a long-existing saying. Arthur Block’s “Murphy’s Law” books gave the proverb a wrong attribution with a misspelled name: “SEGAL’S LAW: A man with one watch knows what time it is. A man with two watches is never sure.”
 
   
Wikipedia: Segal’s law
Segal’s law is an adage that states:
 
“A man with a watch knows what time it is. A man with two watches is never sure.”
 
It refers to the potential pitfalls of having too much conflicting information when making a decision.
 
20 September 1930, San Diego (CA) Union, pg. 4, col. 1:
Confusion.—Retail jewelers assert that every man should carry two watches. But a man with one watch knows what time it is, and a man with two watches could never be sure.
 
23 October 1930, Mason City (IA) Globe-Gazette, pg. 24, col. 4:
Retail jewelers assert that every man should carry two watches. But a man with one watch knows what time it is and a man with two watches could never be sure.—San Diego Union.
 
6 June 1961, Aberdeen (SD) American-News,  ‘Earl Wilson’s New York,” pg. 4, col. 5:
EARL’S PEARLS: It’s possible to possess too much. A man with one watch knows what time it is; a man with two watches is never sure.—Lee Segall, KIXL, Dallas.
 
26 May 1963, Boston (MA) Globe, “My Favorite Jokes” by Lenny Kent, Parade magazine, pg. E8:
A man with one watch knows what time it is. A man with two watches is never sure.
 
Google Books
The Complete Murphy’s Law:
A Definitive Collection
By Arthur Bloch
Los Angeles, CA: Price Stern Sloan
1991
Pg. ?:
SEGAL’S LAW: A man with one watch knows what time it is. A man with two watches is never sure.
   
Google Books
The Routledge Book of World Proverbs
By Jon R. Stone
New York, NY: Routledge
2006
Pg. 431:
Time
A man with a watch knows what time it is; a man with two watches is never sure. (French)
   
Google Books
Magic in Arranged Marriage:
Is It for the West?
By Dr Mahabala Shetty
Bloomington, IN: AuthorHouse
2011
Pg. 188:
There is a Chinese proverb which says: “A man with one watch knows exactly what time it is; a man with two watches is never sure what time it is.”
 
Google Books
Free on Three:
The Wild World of Human Powered Recumbent Tadpole Tricycles
By Steve Greene
Bloomington, IN: iUniverse
2011
Pg. 559:
Albert Einstein once said that a man with one watch always knows what time it is, but a man with two is never sure.