The latest version of the Pandas library can do this for you easily by using the .dt function.
df['just_date'] = df['dates'].dt.date
The above code syntax will return a datetime.date dtype, if you want to have a datetime64 and you can easily normalize the time component to midnight so it will set the given values to 00:00:00:
df['normalised_date'] = df['dates'].dt.normalize()
This keeps the dtype as datetime64 but the display shows just the date value.
Hope this answer helps.