The functionality to make it possible to change the name of an O365 tenant, especially with Sharepoint Online in mind, is being planned. There is no ETA at this time though.
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An error occurred while saving the commentChris Copland commented
Re-iterating Chris O'Connor's comment of 05/03 (or 03/05 depending on your perspective...). Requirement is to set locale (and therefore date and time format) at a tenant level.
Sharing the link to new uservoice item covering this (needs more votes - maybe Microsoft think this has been completed and therefore closed it off).