I want to change the default date format like mm/dd/yy to dd/mm/yy
for en_us locale
in admin as well as front-end.
Don't want to change the locale for that.
To change visible date format in date inputs You need to set proper Interface Locale in the Account Setting.
After that You will see changes on the Edit Product Page.
To change dates in frontend catalog go to: Stores > Configuration > Catalog > Catalog and find Date & Time Custom Options
There you can configure date format on store front catalog.
Stores/Configuration/General/Locale Options, set Locale
and then you go inStores/Configuration/Catalog/Date & Time Custom Options
and set your format @AshishJagnani.