Dates and Times and Strings, Oh My! #

Working with dates & times can be frustrating. Many systems that you may encounter require various formatting for the datetime object. Luckily, Python is really good at handling this.

Wizard of Oz

Lions and tigers and bears, oh my!

datetime #

Python has a module named datetime to working with date and time objects.

# time_now.py
import datetime

now = datetime.datetime.now()
print(type(now))
print("Current datetime = ", now)

today = datetime.datetime.now().date()
print(type(today))
print("Current date = ", today)

current_time = datetime.datetime.now().time()
print(type(current_time))
print("Current time = ", current_time)

You can also create date and time objects by designating the date or time.

# time_create.py
import datetime

                # year, month, day
d = datetime.date(2018, 4, 13)
print(d)

                # hour, minute, second
t = datetime.time(9, 12, 22)
print(t)

                # year, month, day, hour, minute, second
dt = datetime.datetime(2018, 4, 13, 9, 12, 22)
print(dt)

We can also create date objects from a Unix timestamp. A Unix timestamp is the number of seconds since January 1, 1970 at UTC. You can convert a timestamp to date using fromtimestamp() method.

# unix_timestamp.py
from datetime import datetime

timestamp = datetime.fromtimestamp(1326244364)
print( "Date =", timestamp )

strptime #

There are times when you may receive the datetime object as a string. No worries, Python has a robust package for turning a string into a Python datetime object.

The strptime() method takes two arguments:

a string representing date and time
format code for the first argument

# strptime.py
from datetime import datetime

date_string = "21 June, 2018"
print("date_string =", date_string)

date_object = datetime.strptime(date_string, "%d %B, %Y")
print("date_object =", date_object)

strftime #

Likewise, we can take the Python datetime object and turn it into a string.

# strftime.py
from datetime import datetime

# current date and time
now = datetime.now()

t = now.strftime("%H:%M:%S")
print("time:", t)

s1 = now.strftime("%m/%d/%Y, %H:%M:%S")
# mm/dd/YY H:M:S format
print("s1:", s1)

s2 = now.strftime("%d/%b/%Y, %H:%M:%S")
# dd/MMM/YY H:M:S format
print("s2:", s2)

Directive	Meaning	Example
%a	Abbreviated weekday name.	Sun, Mon, …
%A	Full weekday name.	Sunday, Monday, …
%w	Weekday as a decimal number.	0, 1, …, 6
%d	Day of the month as a zero-padded decimal.	01, 02, …, 31
%-d	Day of the month as a number.	1, 2, …, 30
%b	Abbreviated month name.	Jan, Feb, …, Dec
%B	Full month name.	January, February, …
%m	Month as a zero-padded number.	01, 02, …, 12
%-	m Month as a number.	1, 2, …, 12
%y	Year without century as a zero-padded number.	00, 01, …, 99
%-y	Year without century as a number.	0, 1, …, 99
%Y	Year with century as a number.	2013, 2019 etc.
%H	Hour (24-hour clock) as a zero-padded number.	00, 01, …, 23
%-H	Hour (24-hour clock) as a number.	0, 1, …, 23
%I	Hour (12-hour clock) as a zero-padded number.	01, 02, …, 12
%-I	Hour (12-hour clock) as a number.	1, 2, … 12
%p	Locale’s AM or PM.	AM, PM
%M	Minute as a zero-padded number.	00, 01, …, 59
%-M	Minute as a number.	0, 1, …, 59
%S	Second as a zero-padded number.	00, 01, …, 59
%-S	Second as a number.	0, 1, …, 59
%f	Microsecond as a number, zero-padded on the left.	000000 - 999999
%z	UTC offset in the form	+HHMM or -HHMM.
%Z	Time zone name.
%j	Day of the year as a zero-padded number.	001, 002, …, 366
%-j	Day of the year as a decimal number.	1, 2, …, 366
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relativedelta #

Find the difference between two datetime or date objects.

# relativedelta.py
from datetime import datetime
from dateutil.relativedelta import relativedelta

def main():
    birth_date = input('Enter your DOB as mm/dd/YYYY: ')
    print('your age is', age(birth_date))

def age(d):
    dob = datetime.strptime(d, '%m/%d/%Y')
    today = datetime.today()
    age = relativedelta(today, dob)
    return age.years

main()