Datetime

Date arithmetic with timedelta

Once dates are real date or datetime values you can do math with them. timedelta represents a span of time. Add it to shift dates forward or backward, and subtract two dates to get the gap between them.

Once your dates are real datetime objects you can do math with them. The timedelta class represents a span of time, like 7 days or 90 minutes. Add it to shift dates around.

Build a timedelta and add it to a date:

from datetime import date, timedelta
 
today = date(2024, 7, 4)
one_week = timedelta(days=7)
next_week = today + one_week
print(next_week)

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Output

timedelta accepts several keyword arguments. Pass any combination, including fractional values:

# timedelta(days=...,
#   hours=..., minutes=...,
#   seconds=..., weeks=...)
timedelta(days=1, hours=12)

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What will be the output?

from datetime import date, timedelta
d = date(2024, 1, 1)
print(d + timedelta(days=10))

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Use a negative timedelta, or just subtract, to go backwards in time:

from datetime import date, timedelta
 
d = date(2024, 7, 4)
yesterday = d - timedelta(days=1)
print(yesterday)

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Output

What will be the output?

from datetime import date, timedelta
d = date(2024, 3, 15)
print(d - timedelta(days=14))

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Subtract two date or datetime objects and you get a timedelta describing the gap. Read .days off it for an integer number of days.

Compute how many days between two dates:

from datetime import date
 
start = date(2024, 1, 1)
end = date(2024, 12, 31)
gap = end - start
print(gap)
print(gap.days)

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Output

What will be the output?

from datetime import date
a = date(2024, 5, 1)
b = date(2024, 5, 21)
print((b - a).days)

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Datetimes work the same way. Add a timedelta with hours and minutes to shift the time of day too.

A flight leaves at 14:00 and lasts 7h30m:

from datetime import datetime, timedelta
 
depart = datetime(2024, 6, 1, 14, 0)
length = timedelta(hours=7, minutes=30)
arrive = depart + length
print(arrive)

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Output

What will be the output?

from datetime import datetime, timedelta
dt = datetime(2024, 1, 1, 23, 0)
print(dt + timedelta(hours=2))

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What will be the output?

from datetime import date, timedelta
d = date(2024, 6, 1)
print(d + timedelta(weeks=2))

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What will be the output?

from datetime import date
a = date(2024, 1, 1)
b = date(2024, 1, 11)
print((b - a).days)

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What will be the output?

from datetime import datetime, timedelta
a = datetime(2024, 1, 1, 0, 0)
b = datetime(2024, 1, 1, 1, 30)
gap = b - a
print(gap.seconds)

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