How to Compare Dates in Pandas (With Examples)

You can use the following methods to compare dates between two columns in a pandas DataFrame:

Method 1: Add New Column to DataFrame that Shows Date Comparison

df['met_due_date'] = df['comp_date'] < df['due_date']

This particular example adds a new column called met_due_date that returns True or False depending on whether the date in the comp_date column is before the date in the due_date column.

Method 2: Filter DataFrame Based on Date Comparison

df_met_due_date = df[df['comp_date'] < df['due_date']]

This particular example filters the DataFrame to only keep rows where the date in the comp_date column is before the date in the due_date column.

The following examples show how to use each of these methods in practice with the following pandas DataFrame:

import pandas as pd

#create DataFrame
df = pd.DataFrame({'task': ['A', 'B', 'C', 'D'],
                   'due_date': ['4-15-2022', '5-19-2022', '6-14-2022', '10-24-2022'],
                   'comp_date': ['4-14-2022', '5-23-2022', '6-24-2022', '10-7-2022']})

#convert due_date and comp_date columns to datetime format
df[['due_date', 'comp_date']] = df[['due_date', 'comp_date']].apply(pd.to_datetime)

#view DataFrame
print(df)

  task   due_date  comp_date
0    A 2022-04-15 2022-04-14
1    B 2022-05-19 2022-05-23
2    C 2022-06-14 2022-06-24
3    D 2022-10-24 2022-10-07

Example 1: Add New Column to DataFrame that Shows Date Comparison

The following code shows how to add a new column called met_due_date that returns True or False depending on whether the date in the comp_date column is before the date in the due_date column.

import pandas as pd

#create new column that shows if completion date is before due date
df['met_due_date'] = df['comp_date'] < df['due_date']

#view updated DataFrame
print(df)

  task   due_date  comp_date  met_due_date
0    A 2022-04-15 2022-04-14          True
1    B 2022-05-19 2022-05-23         False
2    C 2022-06-14 2022-06-24         False
3    D 2022-10-24 2022-10-07          True

For each row in the DataFrame, the new met_due_date column shows whether the date in the comp_date column is before the date in the due_date column.

For example, we can see that task A had a due date of 4/15/2022 and a completion date of 4/14/2022.

Since the completion date was before the due date, the value in the met_due_date column is True.

Example 2: Filter DataFrame Based on Date Comparison

The following code shows how to filter the DataFrame to only contain rows where the date in the comp_date column is before the date in the due_date column.

import pandas as pd

#filter for rows where completion date is before due date
df_met_due_date = df[df['comp_date'] < df['due_date']]

#view results
print(df_met_due_date)

  task   due_date  comp_date
0    A 2022-04-15 2022-04-14
3    D 2022-10-24 2022-10-07

The new DataFrame has been filtered to only contain rows where the date in the comp_date column is before the date in the due_date column.