When you are using the UK locale with time format MM/DD - and it's properly displaying the date in the console and reports, the date is changed to US format (DD/MM) when saving into Spreadsheet (CSV).
Changes seem to be made somewhere prior to ITMS 8.6 release, as earlier versions the Date format is correct.
ITMS 8.5, 8.6, 8.7
Known issue.
This issue has been addressed under ITMS 8.6 RU2 release.
Refer to the following article:
"Using "Use neutral locale for values" option while exporting a report"