Jira JQL search doesn't respect the ISO8601 and personal settings

Issue Summary

When opening any calendar in the JQL search, the calendar's first date is Sunday, even if the user's personal settings are Europen countries, for example, English Uk
This is reproducible on Data Center: (yes) / (no)

Steps to Reproduce

1. Go to your personal settings
2. Click the profile settings page, change the Language to English UK (for example)
3. Go to Jira and open a ticket
4. Check any date field, the start date of the calendar will be Monday
5. Go to any project > Issues
6. In search click + more and search for the Due date
7. Click Between and open the calendar.
8. Calendar starts on Sunday

Expected Results

The calendar starts on Monday

Actual Results

The calendar starts on Sunday

Workaround

Currently, there is no known workaround for this behaviour. A workaround will be added here when available