Dates and Times

This section discusses the operations on dates and times in the Python standard library.

Basic dates and times

datetime is a module that provides a number of classes for manipulating dates and times. For example, we can use it to create a date object, a time object, or a datetime object.

from datetime import date, time, datetime
d1 = date.today() # today's date
t1 = time(12, 30, 00) # 12:30:00
dt1 = datetime.now() # current date and time
print(d1)
print(t1)
print(dt1)

Results are like this:

2020-11-18
12:30:00
2020-11-18 12:30:00.849000

These objects have some properties that can be accessed. For example, the date object has a year, month, and day property.

print(d1.year)
print(d1.month)
print(d1.day)

The time object has a hour, minute, and second property.

print(t1.hour)
print(t1.minute)
print(t1.second)

The datetime object has a year, month, day, hour, minute, and second property.

print(dt1.year)
print(dt1.month)
print(dt1.day)
print(dt1.hour)
print(dt1.minute)
print(dt1.second)

We can use weekday() to get the day of the week for a date. For example, the day of the week for the date 2020-11-18 is Friday.

days = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
print(days[d1.weekday()])

It will print Friday. The weekday() method returns an integer between 0 and 6, where 0 is Monday and 6 is Sunday.

date, time, and datetime objects are immutable. We need to use the replace() method to create a new object with a different value for one of the properties.

d2 = d1.replace(year=2021)
print(d2)

This will print 2021-11-18. We can also use the replace() method to change the time or datetime object.

Date and time formatting

The main way to format dates and times is to use the strftime() method. For example, we can use the strftime() method to format the date 2020-11-18 as November 18, 2020. For more information, see strftime().

An example of formatting a date, a time and a datetime object:

from datetime import date, time, datetime
d1 = date(2020, 11, 18)
t1 = time(12, 30, 00)
dt1 = datetime(2020, 11, 18, 12, 30, 00)
print(d1.strftime('%B %d, %Y')) # November 18, 2020
print(t1.strftime('%I:%M %p')) # 12:30 PM
print(dt1.strftime('%B %d, %Y %I:%M %p')) # November 18, 2020 12:30 PM

Calculating dates and times

We can perform calculations on dates and times using timedelta(). For example, we can use the timedelta() method to calculate the number of days between two dates. Dates and times can be compared using the <, >, <=, >=, ==, and != operators.

from datetime import date, timedelta
d1 = date(2020, 11, 18)
d2 = date(2020, 12, 20)
delta = d2 - d1 # timedelta
print(delta.days) # days between d1 and d2
print(d1 > d2) # if d1 is after d2
print(d1 <= d2) # if d1 is before or on d2

Output is going to be 32, False, and True. timedelta() can be used to perform date math. An example:

from datetime import date, timedelta
now = datetime.now()
oneyear = timedelta(days=365) # one year, a timedelta object
oneweek = timedelta(weeks=1) # one week, a timedelta object
print(now + oneweek) # prints the datetime one week from now
print(now + oneyear) # prints the datetime one year from now
print(now - oneweek) # prints the datetime one week ago