I was reading note 2246411 - Incorrect data label formatting for some Info Chart types - and it stated that '[w]hen the format string for Info Chart data labels is set to "Default" in the listed chart types [essentially all of them], the date labels are not correctly formatting for the listed charts.'
When I change the format from 'Default' to 'None' my chart looks like this.
which is not necessarily what I want but is definitely better than 0, 1, 1, 2. ...
This is at least a workaround.