Date formatting is changed per-language. For instance, English (US) and Français (Canada) will see a MM/DD/YYYY format.
If you want to view Trello in English, but use international date formatting, you can change your language to English (UK) from English (US).
To change your language, go to your profile page (https://trello.com/u/your/account) click on Account details on Change language, you’ll be redirected to the Atlassian account preferences (you can go directly through this link), where you can change the Language inside Trello, which will change the date formatting.
Setting your account language to English (UK) will cause Trello to show Monday as the first day of the week, shows dates as DD/MM/YYYY, and use 24-hour time.
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