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How to Add Milliseconds to Datetime in Python

Precise time manipulation is essential in many programming tasks.

This guide focuses on adding milliseconds to datetime and time objects in Python, using the timedelta class. We'll explore how to work with existing datetime objects, current time, formatting, and handling cases involving only time components.

Adding Milliseconds to a datetime Object​

You can add milliseconds to a datetime object created from a string using the timedelta() class:

from datetime import datetime, timedelta

date_string = '2024-11-24 09:30:00.000123'
datetime_object = datetime.strptime(date_string, '%Y-%m-%d %H:%M:%S.%f')
result = datetime_object + timedelta(milliseconds=300)
print(result)  # Output: 2024-11-24 09:30:00.300123
  • datetime.strptime() parses the date and time string.
  • The timedelta(milliseconds=300) creates a timedelta object representing a duration of 300 milliseconds.
  • The result shows that 300 milliseconds have been added to the datetime object datetime_object.

Creating datetime Objects and Adding Milliseconds​

You can also add milliseconds to a datetime object constructed directly:

from datetime import datetime, timedelta

dt = datetime(2024, 9, 24, 9, 30, 35)
result = dt + timedelta(milliseconds=400)
print(result)  # Output: 2024-09-24 09:30:35.400000

Adding Milliseconds to the Current Time​

To add milliseconds to the current time, use datetime.today() to get a datetime object:

from datetime import datetime, timedelta

current_time = datetime.today()
result = current_time + timedelta(milliseconds=500)
print(result) # Output (Will depend on the current date and time, but with milliseconds added)
  • datetime.today() gets the current date and time. timedelta is used to add the milliseconds, and updates the seconds, minutes, etc. as needed.

Adding Milliseconds to a time Object​

If you have just a time object, you can't directly add timedelta as time objects store only the time component. Use datetime.combine() to get a datetime object:

from datetime import datetime, date, timedelta, time

t = time(6, 25, 30, 123) # time object
result = datetime.combine(date.today(), t) + timedelta(milliseconds=400)
print(result) # Output (Will vary depending on current date)
only_time = result.time()
print(only_time)  # Output: 06:25:30.400123
  • datetime.combine() creates a datetime object from today's date combined with t.
  • timedelta is added to the combined datetime object.
  • result.time() extracts the time part after adding the milliseconds.

Extracting Time Components​

Use the .time() method to get the time component of a datetime object:

from datetime import datetime, date, timedelta, time

t = time(6, 25, 30, 123)
result = datetime.combine(date.today(), t) + timedelta(milliseconds=400)
only_t = result.time()
print(only_t)  # Output: 06:25:30.400123

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