CLM utilizes Dojo and in Dojo the date format is driven by locale.
http://dojotoolkit.org/reference-guide/1.8/quickstart/internationalization/specifying-locale.html#id3
In other words, the date format is changed dynamically according to the browser language setting. But I have not fount any locale with a default date format of "yyyy/mm/dd". Most of the locales use "MM" which means the name of the month where "mm" means the number of the month.
If the date format is not the one that you want when the language setting is correct for you, then you may be out of luck I'm afraid.
By the way, the "default", or "fall-back" language setting is English (United States).