Refreshing Members page decreases expiration date of roles

Summary

Refreshing the Members page of a repository causes any Expiration Dates to decrease by one day.

Steps to reproduce

1. Create a repository (privacy doesn't seem to matter)
2. Add a member (it doesn't seem to matter who), and specify an expiration date. It doesn't seem to matter what the date is. Role also seems to have no effect.
3. Refresh the page. You should see the expiration date of that person's access decrease by one day. Repeat ad nauseam. Note that navigating away and back doesn't seem to decrease the date, it appears you have to refresh the page.

Example Project

https://gitlab.com/szabado/example

What is the current bug behavior?

The expiration date decreases by one day.

What is the expected correct behavior?

The expiration date stays the same.

Output of checks

This bug happens on GitLab.com

Other Information

I'm running Firefox 60.0.2 on Ubuntu 17.10 (no clue if it makes a difference).