How to Perform Date and Time Calculations in Python?

Performing date and time calculations in Python is very easy using timedelta objects. Whenever you want to add or subtract a date/time, use datetime.datetime() and then add or subtract a datetime.timedelta() instance. A timedelta object represents a duration, that is, the difference between two dates or times. The timedelta constructor has the following function signature –

datetime.timedelta([days[, seconds[, microseconds[, milliseconds[, minutes[, hours[, weeks]]]]]]])

Note: All parameters are optional and default to 0. Parameters can be of type int, long, or float and can be positive or negative. You can learn more here – https://docs.python.org/2/library/datetime.html#timedelta-objects

For more Python-related articles, read: Python Tutorial

Example

An example of timedelta objects and dates –

import datetime
old_time = datetime.datetime.now()
print(old_time)
new_time = old_time - datetime.timedelta(hours=2, minutes=10)
print(new_time)

Output

This will give the output –

2018-01-04 11:09:00.694602
2018-01-04 08:59:00.694602

timedelta() does not support arithmetic operations with datetime.time() objects; if you need to use an offset from an existing datetime.time() object, use datetime.datetime.combine() to form a datetime.datetime() instance, perform the calculation, and then use the .time() method to extract the time again.

Subtracting two datetime objects produces a timedelta object. This timedelta object can be used to find the exact difference between two dates.

Example

t1 = datetime.datetime.now()
t2 = datetime.datetime.now()
print(t1 - t2)
print(type(t1 - t2))

Output

This will give the output –

-1 day, 23:59:56.653627
<class 'datetime.timedelta'>