Display date suggestions as dd/mm/yyyy or DD/MM/YYYY

I have found a lot of posts regarding how to display the order of a date (MM/DD/YYYY vs DD/MM/YYYY) but I haven't found any regarding how to display a "This is how your date should look" hint to a user. Below is an example of how I am currently displaying this hint to a user.

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I am wondering if there is some sort of standard regarding how to display this hint to a user? Or if I can do whatever I like as long as I am consistent throughout my project

All lower case:

dd/mm/yyyy mm/dd/yyyy mmyyyy ddmmyyyy

All upper case:

DD/MM/YYYY MM/DD/YYYY MMYYYY MMDDYYYY

Capital month:

dd/MM/yyyy MM/dd/yyyy MMyyyy ddMMyyyy

Displaying inconsistently, but may be visually appealing for its condition

dd/mm/yyyy mm/dd/yyyy MMYYYY ddMMyyyy

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