I have a dataframe ready to be used in different models. like below

Now I want to add another column to this data frame known as "Date time". The column seems ok before adding it.

When I try to add this column to the dataframe through this line df1['date'] = date it shows that there are NaN in the column which is wrong because I have checked and there is not NaN in that. I did "reset index" but again faced the same issue.
