"Time Since Chart" and other dashboard gadgets do not respect JIRA's ISO8601 setting

Issue Summary

"Time Since Chart" and other gadgets like the Time to First response gadget, do not respect JIRA's ISO8601 setting.

Steps to Reproduce

1. Navigate to Jira System > Look and Feel
2. Enable the "Use ISO8601 standard in Date Picker"
3. Navigate to Dashboard and add a Gadget: "Time Since Chart"/"Time to First response
4. Customize the gadget and set it on a weekly basis

Expected Results

The week number goes according to the ISO8601 standard.

Actual Results

The gadgets seem to be one week off indicating one week more than what it should.

• In the example indicated here if you check ISO8601 week difference attachment, according to ISO8601 the week between 1st to 7th Feb 2021 should be Week 5 but the gadget shows it as Week6.

Workaround

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