How to convert datetime object to milliseconds

Question

I am parsing datetime values as follows:

df['actualDateTime'] = pd.to_datetime(df['actualDateTime'])

How can I convert this datetime objects to milliseconds?

I didn't see mention of milliseconds in the doc of to_datetime.

Update (Based on feedback): This is the current version of the code that provides error TypeError: Cannot convert input to Timestamp. The column Date3 must contain milliseconds (as a numeric equivalent of a datetime object).

import pandas as pd
import time

s1 = {'Date' : ['2015-10-20T07:21:00.000','2015-10-19T07:18:00.000','2015-10-19T07:15:00.000']}

df = pd.DataFrame(s1)

df['Date2'] = pd.to_datetime(df['Date'])

t = pd.Timestamp(df['Date2'])

df['Date3'] = time.mktime(t.timetuple())

print df

Answer 1

Timestamps in pandas are always in nanoseconds.

This gives you milliseconds since the epoch (1970-01-01):

df['actualDateTime'] = df['actualDateTime'].astype(np.int64) / int(1e6)

Answer 2

This will return milliseconds from epoch

timestamp_object.timestamp() * 1000