Fandango says 10/27/96
I wonder if this is a time zone issue. If he died after 10 pm in LA on 10/27/96, the date would be 10/28/96 for eastern time zones.
The Independent (in the UK) also says 10/28.
The UPI also has it as 10/28
I can't find a definitive answer.
Morey AmsterdamDate of Death: 28 October 1996, Los Angeles, California, USA
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Death: Oct. 27, 1996
Los Angeles County
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Also wrong ?
(born Moritz Amsterdam, December 14, 1908 – October 27, 1996)
Amsterdam died of a heart attack at Cedars Sinai Hospital in Los Angeles, California
on October 28, 1996, at the age of 87
Some newspaper obits from October 29, 1996 (Los Angeles Times and the Washington Post, for example) reported his death as Monday, October 28th instead of Sunday, October 27th. Considering the headstone you posted, it's certainly possible that those newspaper articles reported the wrong death date.
If you haven't done so, I would suggest submitting an update by correcting the date of death and indicate that the date comes from his headstone and see if the IMDb accepts the date, which may take 2-3 days (or more) to process.
I hope this helps. Please write back if you have any more questions.