Python Pandas - How to Round the TimeDeltaIndex with milliseconds frequency

To round the TimeDeltaIndex with milliseconds frequency, use the TimeDeltaIndex.round() method. For milliseconds frequency, use the freq parameter with value 'ms'.

Creating a TimeDeltaIndex

First, import pandas and create a TimeDeltaIndex with timedelta-like data ?

import pandas as pd

# Create a TimeDeltaIndex object with different time formats
tdIndex = pd.TimedeltaIndex(data=['10 day 5h 2 min 3us 10ns', '+22:39:19.999999',
                                  '2 day 4h 03:08:02.000045', '+07:20:32.261811624'])

print("TimedeltaIndex...\n", tdIndex)

TimedeltaIndex...
 TimedeltaIndex(['10 days 05:02:00.000003010', '0 days 22:39:19.999999',
                '2 days 07:08:02.000045', '0 days 07:20:32.261811624'],
               dtype='timedelta64[ns]', freq=None)

Viewing Components

You can examine the individual components (days, hours, minutes, etc.) of the TimeDelta values ?

import pandas as pd

tdIndex = pd.TimedeltaIndex(data=['10 day 5h 2 min 3us 10ns', '+22:39:19.999999',
                                  '2 day 4h 03:08:02.000045', '+07:20:32.261811624'])

print("The Dataframe of the components of TimeDeltas...\n", tdIndex.components)

The Dataframe of the components of TimeDeltas...
   days  hours  minutes  seconds  milliseconds  microseconds  nanoseconds
0    10      5        2        0             0             3           10
1     0     22       39       19           999           999            0
2     2      7        8        2             0            45            0
3     0      7       20       32           261           811          624

Rounding to Milliseconds

Use the round() method with freq='ms' to round to the nearest millisecond ?

import pandas as pd

tdIndex = pd.TimedeltaIndex(data=['10 day 5h 2 min 3us 10ns', '+22:39:19.999999',
                                  '2 day 4h 03:08:02.000045', '+07:20:32.261811624'])

print("Original TimedeltaIndex...")
print(tdIndex)

print("\nAfter rounding to milliseconds frequency...")
rounded_td = tdIndex.round(freq='ms')
print(rounded_td)

Original TimedeltaIndex...
TimedeltaIndex(['10 days 05:02:00.000003010', '0 days 22:39:19.999999',
               '2 days 07:08:02.000045', '0 days 07:20:32.261811624'],
              dtype='timedelta64[ns]', freq=None)

After rounding to milliseconds frequency...
TimedeltaIndex(['10 days 05:02:00', '0 days 22:39:20',
               '2 days 07:08:02', '0 days 07:20:32.262000'],
              dtype='timedelta64[ns]', freq=None)

How Rounding Works

The rounding operation follows standard rounding rules:

• Values less than 0.5ms are rounded down (truncated)
• Values 0.5ms and above are rounded up to the next millisecond
• Microseconds and nanoseconds are removed in the process

Conclusion

Use TimeDeltaIndex.round(freq='ms') to round time deltas to millisecond precision. This removes microseconds and nanoseconds while following standard rounding rules for fractional milliseconds.