“Boss: You should have been here at 8:30! Employee: Why, what happened at 8:30?”

An employment joke about a late employee is:
 
Boss: You should have been here at 8:30!
Employee: Why? What happened at 8:30?
 
The joke was printed in many newspapers in 1935.
 
           
20 March 1935, San Diego (CA) Union, “The Northeast Corner,” pg. 4, col. 6:
“I want to tell you, miss that you should have been here at nine o’clock,” said the office manager as the new stenog breezed in, merrily cracking her gum.
 
“Is that so?” she asked cheerily. What happened at that time?
   
31 March 1935, The Sunday Star (Washington, DC), “Moon Mullins” comic strip by Frank Willard, comics sec., pg. 1, col. 3:
Boss: MULLINS! YOU SHOULD HAVE BEEN HERE AT EIGHT O’CLOCK!
Moon Mullins: YES, SIR.
Kayo Mullins: WHY? WHAT HAPPENED?
 
15 May 1935, The Daily News (Frederick, MD), “Mutt and Jeff” comic strip by Bud Fisher, pg. 10, col. 2:
Boss: YOU’RE LATE! YOU SHOULD HAVE BEEN HERE AT SEVEN O’CLOCK.
Jeff: WHY, WHAT HAPPENED, BOSS!
(At home.—ed.)
Mutt: WELL, HOW’S THE NEW JOB COMIN’ ALONG?
Jeff: It AIN’T! I QUIT!
Mutt: YOU QUIT? WHY?
Jeff: THE BOSS SAID SOMETHING I DIDN’T LIKE!
Mutt: WHAT DID HE SAY?
Jeff: HE SAID “YOU’RE FIRED!” SO I QUIT!
   
30 May 1935, Jeffersonian Democrat (Brookville, PA), pg. 4, col. 8:
What!
Boss (to office boy who is half an hour late)—“You should have been here at eight o’clock.”
Office Boy—“Why? What happened?”
Peterson’s Weekly, London.
 
25 October 1936, Ogden (UT) Standard-Examiner, Neal O’Hara column, comics sec., pg. 1, col. 2:
FAVORITE GAG
Today’s favorite gag: Boss (severely)—“You should have been here at nine o’clock.” New employe—“Why? What happened?”
 
2 November 1981, Dallas (TX) Morning News, “Oy vey, such a book this man has written” by Philip Wuntch, pg. 1C, col. 5:
Shapiro walks into work one day at nine, half an hour late. The boss is furious. “You should have been here at 8:30!” he shouts. “Why?” asks Shapiro. What happened at 8:30?”
 
Google Books
Holy Days and Holidays:
Blessed Occasions for Heart and Mind
By George P. Bendall
Marina del Rey, CA: DeVorss Publications
1995
Pg. 22:
We miss so much by not being good to ourselves, like the employee whose boss scowled at him when he came in late and said, “You should have been here at nine!” The employee said, “Why? What happened at nine?”
 
Google Groups: alt.gossip.celebrities
PRINT SOUP…06/17
AGC Queen
6/17/99
E! ONLINE….PRINT SOUP….06/17
(...). Jump to the 75 funniest jokes of all time (“A man walks into work at 9 o’clock. The boss screams, “You should have been here at 8:30!” Man: “Why? What happened at 8:30?”) and find out why your favorite comics all consider Sam Kinison a genius.
   
Google Groups: rec.humor.jewish
On-time
Renee
8/25/99
Shapiro was late to work, so his boss yelled
“You should have been here at eight-thirty!”
Shapiro replied “Why?  What happened at eight-thirty?”
 
Google Groups: alt.humor.puns
Puns of the Weak 8/10/01
Stan Kegel
8/11/01
(...)
A guy shows up late for work. The boss yells “You should have been here at 8:30!” He replies : “Why? What happened at 8:30?” (Bruce H. G. Calder)
 
Twitter
WildMountainGourmet
@WildMountain
Replying to @olivejoose
@natBerry A guy shows up late for work. The boss yells “You should have been here at 8:30!” he replies: “Why? What happened at 8:30?”
9:31 AM - 24 Apr 2009
 
Twitter
FunnyOneLiners
@Funnyoneliners
A guy shows up late for work. His boss yells “You should have been here at 8:30!” He: “Why? What happened at 8:30?”
10:09 AM - 15 Jun 2009
   
Google Books
The Everything Big Book of Jokes
By Evan C. Thomas
Avon, MA: Adams Media
2014
Pg. 113:
A BOSS CATCHES AN EMPLOYEE walking in the door at 10 a.m. The boss is angry and barks at the employee, “You should have been here at 8 a.m.!”
 
“Why?” the employee asks. “What happened at eight?”
 
Twitter
Beardedhipster
@ABeardedhipster
A guy shows up late for work.
The boss yells, “You should have been here at 8:30!”
The guy replies: “Why? What happened at 8:30?”
2:12 PM - 20 Jul 2018
 
Pueblo (CO) Chieftain
Monday Medley
July 23, 2018
(...)
Here’s a work-appropriate joke to get your funny started: A guy arrives late to work. The boss yells, “You should have been here at 8:30.” The guy responds, “Why? What happened at 8:30?”