How can I calculate the age of a person (based off the dob column) and add a column to the dataframe with the new value?

dataframe looks like the following:

```
    lname      fname     dob
0    DOE       LAURIE    03011979
1    BOURNE    JASON     06111978
2    GRINCH    XMAS      12131988
3    DOE       JOHN      11121986

```

I tried doing the following:

```
now = datetime.now()
df1['age'] = now - df1['dob']

```

But, received the following error:

TypeError: unsupported operand type(s) for -: 'datetime.datetime' and 'str'