I have two dataframes and want to compare them and delete the days in the df2 which are not the same as in df1. I tried to use: 

```
df2[~df2.Date.isin(df1.Date)]

```

but this does not work and getting an empty dataframe. df2 should look like df1. The dataframe's looks like the following:

```
df1
        Date
0    20-12-16
1    21-12-16
2    22-12-16
3    23-12-16
4    27-12-16
5    28-12-16
6    29-12-16
7    30-12-16
8    02-01-17
9    03-01-17
10   04-01-17
11   05-01-17
12   06-01-17

df2

         Date
0    20-12-16
1    21-12-16
2    22-12-16
3    23-12-16
4    24-12-16
5    25-12-16
6    26-12-16
7    27-12-16
8    28-12-16
9    29-12-16
10   30-12-16
11   31-12-16
12   01-01-17
13   02-01-17
14   03-01-17
15   04-01-17
16   05-01-17
17   06-01-17

```