Unable to change clock separator I am using OS X Yosemite 10.10.3. In the Language &amp; Region preferences, I clicked Advanced and set my clock format to 0-23:08.
However, the clock in the menu bar and in the Date &amp; Time preferences is displayed with the . separator instead of :. The dot seems to be the default for my language format (which is wrong, we use :). Furthermore, if I modify the contents of com.apple.menuextra.clock.plist, they are overridden as soon as I restart SystemUIServer or relogon. For example:

defaults write com.apple.menuextra.clock DateFormat -string 'H:mm'
killall SystemUIServer
defaults read com.apple.menuextra.clock


results in

{
    DateFormat = "HH.mm";
    FlashDateSeparators = 0;
    IsAnalog = 0;
}


How can I change the clock separator?
I had the same problem, I solved it by go to Language &amp; Region and choose the region that has the same clock separator (I chose Australia) and then you can go to Advanced and customize your own dates and times format. Hope it helps