Wrong month abbreviations used for Deutsch language on different pages

Summary

On different pages there are different month abbreviations used in date displaying and date pickers.

Environment

Jira Core 7.13.0, Jira Core 8.0.0-m0021

Steps to Reproduce

1. Start Jira Core 7.13.0 with: mvn amps:run-standalone -Dproduct=jira -Dproduct.version=7.13.0
2. Setup Jira with defaults and create sample project and issue
3. Got to user preferences and switch language to: Deutsch (Deutschland)
4. Navigate to sample issue detailed view (e.g. http://localhost:2990/jira/browse/DEMO-1)
5. Click Edit and set due date to 10.03.2019. After selecting in date picker the input value is 10/Mrz/19 (screenshot1)
6. Save Issue. On issue view you can see due date as 10/Mär/19 (screenshot2)
7. Go to project versions administration view (e.g. http://localhost:2990/jira/plugins/servlet/project-config/DEMO/administer-versions?status=unreleased)
8. Add new version with start date equal;l to 10.03.2019. After selecting in date picker the input value is 10/mär/19. (screenshpot3)
9. Save version. On version list you can see start date as 10/Mär/19 (screenshot4)

Expected Results

Different pages and components use different formats: 10/Mrz/19,  10/Mär/19, **10/mär/19

Actual Results

All dates in Jira system for logged-in user should use the same format, language and month names/abbreviations. E.g. Jira should use everywhere on pages and in components: 10/Mär/19

Workaround

None

Quick investigation

On Jira issue view:
console.log(Calendar._SMN) > ["Jan", "Feb", "Mrz", "Apr", "Mai", "Jun", "Jul", "Aug", "Sep", "Okt", "Nov", "Dez"]

On project versions administration view:
console.log(Calendar._SMN) > ["Jan", "Feb", "Mär", "Apr", "Mai", "Jun", "Jul", "Aug", "Sep", "Okt", "Nov", "Dez"]