datetime.timedelta()

from datetime import datetime, timedelta

# Create a duration object.
delta = timedelta(days=days, hours=hours, minutes=minutes, seconds=seconds, weeks=weeks)

# Add a duration to a datetime to get a future datetime.
future = dt + delta

# Subtract a duration from a datetime to get a past datetime.
past = dt - delta

# Subtract two datetimes to get the difference as a timedelta.
diff = datetime_a - datetime_b

from datetime import datetime, timedelta

# Calculate the datetime 7 days from now.
now = datetime.now()
one_week_later = now + timedelta(weeks=1)
print(one_week_later.strftime('%Y-%m-%d'))  # Prints the date one week from today.

# Calculate the datetime 30 days ago.
thirty_days_ago = now - timedelta(days=30)
print(thirty_days_ago.strftime('%Y-%m-%d'))  # Prints the date 30 days ago.

# Combine multiple units in a single calculation.
deadline = now + timedelta(days=3, hours=5, minutes=30)
print(deadline.strftime('%Y-%m-%d %H:%M'))  # Prints the deadline datetime.

# Find the difference between two datetimes.
birthday = datetime(2000, 1, 1)
today = datetime.now()
diff = today - birthday
print(f'{diff.days} days have passed.')  # Prints the number of elapsed days.

# Get the total duration in seconds using total_seconds().
delta = timedelta(hours=2, minutes=30)
print(delta.total_seconds())  # Prints '9000.0' (2.5 hours × 3600 seconds).

# Calculate the time remaining until an event.
event = datetime(2025, 12, 31, 23, 59, 59)
remaining = event - datetime.now()
if remaining.days >= 0:
    print(f'{remaining.days} days until the event.')

# You can also perform arithmetic between two timedelta objects.
d1 = timedelta(days=5)
d2 = timedelta(days=3)
print(d1 + d2)          # Prints '8 days, 0:00:00'.
print(d1 - d2)          # Prints '2 days, 0:00:00'.
print(d1 * 2)           # Prints '10 days, 0:00:00'.

'timedelta' is produced automatically when you subtract two datetime objects. For example, the result of 'datetime_a - datetime_b' is a 'timedelta' object. This makes it straightforward to calculate things like the number of days since a birthday, the days remaining until an event, or the total duration of a task.

'timedelta.days' and 'timedelta.seconds' return the individual components of a duration. For example, 'timedelta(hours=25)' gives a 'days' value of '1' and a 'seconds' value of '3600'. When you need the total duration in seconds, always use 'total_seconds()' instead of calculating from 'days' and 'seconds' separately.

To create datetime objects, see 'datetime.datetime() / datetime.date() / datetime.time()'. For formatting and parsing, see 'datetime.strftime() / datetime.strptime()'.