Why is Excel not recognizing my custom date formats after I paste data into my sheet?

1. Check column formats – make sure the column is properly formatted as a date and has the correct date format set.
2. Check for spaces – If the data includes leading or trailing spaces, these can be misinterpreted as dates.
3. Check for merged cells – The date format cannot be retained for merged cells.
4. Check for duplicates – If there are duplicate values, this can be interpreted as a date.
5. Check for text in another language – Text in a different language can be interpreted as a date.