I understand that you want to change the date format and time columns for the SharePoint site. Here are two options:
1.You can change the presentation view in SharePoint Designer to format the date and time column. Change the formula to ddwrt: FormatDate (line ($ thisNode / @ * [name () = current () / @ Name]), 1033.7).
2.You can change the regional settings for the site collection. Change the locale in other countries, the date format will automatically change for all existing data and time columns.
I tried with a German and its date and time format is similar to dd mm yyyy.
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