With the Feb 2018 update the date slicers like the mobile app on android are now all US format. There is no way to change this even with my regional settings set to uk and my laptop language set to UK???
This is particularly annoying. Also I cannot format dates to dd/MM/yyyy either that was broken in Jan 2018 update?
I'm in Australia and we use the same format as you, and I use the Power Bi service via Google Chrome. I had your issue for many months. To fix it, in Google Chrome settings make sure that the language is set to "English (United Kingdom)" and is set to "Display Google Chrome in this language". Then go to your Power Bi Service settings and from the settings menu select General>Language> and make sure you select "Default (browser langauage)". You might have to log out and log back in but it worked for me. (update: I've since changed my chrome setting to "English (Australia)" as I don't want to risk my currency field format switching from $ to £)
Thanks Warrenz your suggestion worked for me (eventually). I say eventually because even though I set my language in Google Chrome settings to English (Australia) it wasn't at the top of the list so make sure you have it at the top of the list if you have more than one language. This can be achieved by clicking on the elipses to the right of the language that you want to move and select 'move to top'.