Pandas datetime inconsistent format

I hope someone can help me with the following: I'm trying to convert my data to daily averages using:

df['timestamp'] = pd.to_datetime(df['Datum WSM-09'])
df_daily_avg = df.groupby(pd.Grouper(freq='D', key='timestamp')).mean()

df['Datum WSM-09'] looks like this:

0          6-3-2020 12:30
1          6-3-2020 12:40
2          6-3-2020 12:50
3          6-3-2020 13:00
4          6-3-2020 13:10
               ...       
106785    18-3-2022 02:00
106786    18-3-2022 02:10
106787    18-3-2022 02:20
106788    18-3-2022 02:30
106789    18-3-2022 02:40
Name: Datum WSM-09, Length: 106790, dtype: object

However, when executing the first line the data under "timestamp" is inconsistent. The last rows displayed in the picture are correct. For the first ones, it should be 2020-03-06 12:30. The month and the day are switched around.

Many thanks

Solution

Try using the "dayfirst" option:

df['timestamp'] = pd.to_datetime(df['Datum WSM-09'], dayfirst=True)