Data truncation: Incorrect datetime value: '7/21/15' for column 'announced_on' at row 1
the normal date format is 2020-04-19.

If you try to insert 7/21/15 into a date field this will fail as you noticed.

Most imports allow to reformat input.

In mysql you would use STR_TO_DATE('7/21/15', '%m/%e/%y') to import data.

If you don't want to rewrite or need the dates that way , you could define the field as varchar(10) that is big enough to hold it.