Summary

An incorrect week number is shown in JIRA's date picker control. The problem occurs because Jira marked the same week as last week of year Y and first week of year Y+1.

Steps to reproduce

1. Open the date picker and go to the last week in the year, for example last week in 2020.
2. Note which week is last.
3. Move to the next week, which is the first week of the following year, for example first week in 2021.

Expected Result
Week 1 2021 should not be the same as week 53 2020. Week 1 2021 should start on Sun Jan 3 and finish on Sat Jan 9.

Actual Result
Week 1 2021 is the same as week 53 2020, which is the week starting on Sun Dec 27 and finishing on Sat Jan 2.