Warning 1292 "Incorrect date value:"

Hello Everyone,

I have been trying to find information about this issue in the
documentation and have not been able to. I hope someone can help.

I built a web-based app (PHP) that allows users to upload the contents
of a CSV file into database tables.

My users have reported that most of the time, everything is fine, but
some records do not show up. Although I can see the records by doing
a SELECT with the mysql interface, I cannot delete these records in
question. When I try to delete them 0 rows are affected and I get
this warning:

+---------+------
+----------------------------------------------------------- -----+
| Level | Code |
Message |
+---------+------
+----------------------------------------------------------- -----+
| Warning | 1292 | Incorrect date value: '1987' for column
'Sample_Date' at row 1 |
+---------+------
+----------------------------------------------------------- -----+

I haven't been able to find out what this warning means. I don't know
how to proceed here.

Any ideas, comments would be appreciated.

Thanks,
Andy