Times and dates

The datetime object

The Python datetime module includes the function now, which returns a datetime object containing the current date and time. The default printout of a datetime object looks like this:

from datetime import datetime

my_time = datetime.now()
print(my_time)

You can also define the object yourself:

from datetime import datetime

my_time = datetime(1952, 12, 24)
print(my_time)

By default, the time is set to midnight, as we did not give a time of day in the example above.

Different elements of the datetime object can be accessed in the following manner:

from datetime import datetime

my_time = datetime(1952, 12, 24)
print("Day:", my_time.day)
print("Month:", my_time.month)
print("Year:", my_time.year)

A time of day can also be specified. The precision can vary, as you can see below:

from datetime import datetime

pv1 = datetime(2021, 6, 30, 13)     # 30.6.2021 at 1PM
pv2 = datetime(2021, 6, 30, 18, 45) # 30.6.2021 at 6.45PM

Compare times and calculate differences between them

The familiar comparison operators work also on datetime objects:

from datetime import datetime

time_now = datetime.now()
midsummer = datetime(2021, 6, 26)

if time_now < midsummer:
    print("It is not yet Midsummer")
elif time_now == midsummer:
    print("Happy Midsummer!")
elif time_now > midsummer:
    print("It is past Midsummer")

The difference between two datetime objects can be calculated simply with the subtraction operator:

from datetime import datetime

time_now = datetime.now()
midsummer = datetime(2021, 6, 26)

difference = midsummer - time_now
print("Midsummer is", difference.days, "days away")

NB: the result of the datetime subtraction is a timedelta object. It is less versatile than the datetime object. For instance, you can access the number of days in a timedelta object, but not the number of years, as the length of a year varies. A timedelta object contains the attributes days, seconds and microseconds. Other measures can be passed as arguments, but they will be converted internally.

Similarly, addition is available between datetime and timedelta objects. The result will be the datetime produced when the specified number of days (or weeks, seconds, etc) is added to a datetime object:

from datetime import datetime, timedelta
midsummer = datetime(2021, 6, 26)

one_week = timedelta(days=7)
week_from_date = midsummer + one_week

print("A week after Midsummer it will be", week_from_date)

long_time = timedelta(weeks=32, days=15)

print("32 weeks and 15 days after Midsummer it will be", midsummer + long_time)

Let's see how a higher precision works:

time_now = datetime.now()
midnight = datetime(2021, 6, 30)
difference = midnight - time_now
print(f"Midnight is still {difference.seconds} seconds away")

Formatting times and dates

The datetime module contains a handy method strftime for formatting the string representation of a datetime object. For example, the following code will print the current date in the format dd.mm.yyyy, and then the date and time in a different format:

from datetime import datetime

my_time = datetime.now()
print(my_time.strftime("%d.%m.%Y"))
print(my_time.strftime("%d/%m/%Y %H:%M"))

Time formatting uses specific characters to signify specific formats. The following is a list of a few of them (please see the Python documentation for a complete list):

You can also specify the delimiter between the different elements, as seen in the examples above.

Datetime formatting works in the reverse direction as well, in case you need to parse a datetime object from a string given by the user. The method strptime will do just that:

from datetime import datetime

birthday = input("Please type in your birthday in the format dd.mm.yyyy: ")
my_time = datetime.strptime(birthday, "%d.%m.%Y")

if my_time < datetime(2000, 1, 1):
    print("You were born in the previous millennium")
else:
    print("You were born during this millennium")

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