"Last Seen" date uses UTC instead of local time zone

### Reproduction Steps

1. Set the WordPress time zone in the general settings to UTC+12.
1. View the LifterLMS reporting page that lists students. `/wp-admin/admin.php?page=llms-reporting`
1. Set the WordPress time zone in the general settings to UTC-12.
1. View the LifterLMS reporting page that lists students. `/wp-admin/admin.php?page=llms-reporting`

### Expected Behavior

The "Last Seen" date should be different between the two page views.

### Actual Behavior

The "Last Seen" date is the same between the two page views.

This issue has been recreated:
+ [x] Locally
+ [ ] On a staging site
+ [ ] On a production website
+ [ ] With only LifterLMS and a default theme

Start at /wp-admin/admin.php?page=llms-reporting and trace where the students list formats the “Last Seen” value. Reproduce the issue with WordPress time zones UTC+12 and UTC-12; done when the displayed date changes appropriately between those views and the existing reporting behavior remains intact.

Written by the indexing model from the issue text.