[M T]

Don't ask me why San Diego reported a negative number of deaths in late April.

I think you mean "Don't ask me why the NYTimes is reporting a negative number of deaths in late April in San Diego."

San Diego's current data is here.  (The earliest archive.org copy is May 8 which has a few but not many differences) The LA Times keeps their own copy.

The LA Times copy shows (for instance) 15 deaths around April 20 and again a week or so in May.  The San Diego data does not show that (single daily maximum is 10).   The San Diego data is by date of death.  My guess is the LA Times is by date of announcement.  I can think of a few reasons the NYT would have to correct their data and might choose to do so by having a negative count.

[M T]

Don't ask me why San Diego reported a negative number of deaths in late April.

I think you mean "Don't ask me why the NYTimes is reporting a negative number of deaths in late April in San Diego."

San Diego's current data is here.  (The earliest archive.org copy is May 8 which has a few but not many differences) The LA Times keeps their own copy.

The LA Times copy shows (for instance) 15 deaths around April 20 and again a week or so in May.  The San Diego data does not show that (single daily maximum is 10).   The San Diego data is by date of death.  My guess is the LA Times is by date of announcement.  I can think of a few reasons the NYT would have to correct their data and might choose to do so by having a negative count.