File dates in the Canvas Files picker do not always show correct dates

**Describe the bug**
When PDFs are added to Canvas Files before 2020, the Canvas Picker shows the file dates as being in the year 2020. This probably appears to be intermittent (see screen shots).

**To Reproduce**
Steps to reproduce the behavior:
1. Go into our Canvas instance, into a course like Literature 404
2. Click on Files and note the "Date Modified" dates
3. Create an assignment and use the Canvas Files picker
4. Check visible dates against the dates in Files.

**Expected behavior**
The Modified dates should match.

**Screenshots**
- From our Lit 404 class -
Files:

Picker:

- From user's class -
Files:

Picker:

**Desktop (please complete the following information):**
- OS: Mac Mojave 10
- Chrome 81

Start by reproducing the mismatch between dates in Canvas Files and the Canvas Files picker using the listed course and assignment steps. Compare the picker’s displayed Modified dates with Files, and consider the issue done when dates for older PDFs match in both views.

Written by the indexing model from the issue text.