Excel parses text filter as a date

I have a spreadsheet that includes a column of dates in a format that Excel doesn't recognize, so I'm treating them as text. I created a Text Filter to select values that begin with 2017-01-1. It selected 0 rows, even though the column includes cells that start with 2017-01-1. I brought the Custom AutoFilter dialog box back up, and found that Excel had changed 2017-01-1 to 1/1/2017. This is a bug: it's a text filter, not a date filter, so it should not be parsing 2017-01-1 as a date.