Pressing the Red Button

Using the built-in modules datetime and timedelta, you can perform date and time addition/subtraction in python:

from datetime import datetime
from datetime import timedelta

#Add 1 day
print datetime.now() + timedelta(days=1)

#Subtract 60 seconds
print datetime.now() - timedelta(seconds=60)

#Add 2 years
print datetime.now() + timedelta(days=730)

#Other Parameters you can pass in to timedelta:
# days, seconds, microseconds, 
# milliseconds, minutes, hours, weeks

#Pass multiple parameters (1 day and 5 minutes)
print datetime.now() + timedelta(days=1,minutes=5)

Here is a python reference that gives more examples and advanced features:
http://docs.python.org/library/datetime.html

If you are coming from a .net or sql environment, here are the above examples in C# and SQL (Microsoft) for comparison:
C#

DateTime myTime = new DateTime();

--Add 1 day
myTime.AddDays(1);

--Subtract 60 seconds
myTime.AddSeconds(-60);

--Add 2 years
myTime.AddYears(2);

SQL

--Add 1 day
select DATEADD(day, 1, getdate())

--Subtract 60 seconds
select DATEADD(second, -60, getdate())

--Add 2 years
select DATEADD(Year, 2, getdate())