Dates in a database aren't stored with any format, unless they are stored as strings - which you say you aren't doing. Instead, they are stored as a number of microseconds since an arbitrary point in time.
They only acquire a format when you convert them to a string for presentation - which would normally be done in presentation software rather than in SQL so that it is in the format preferred by the user.
But you can select the format for the string in SQL:
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