Python datetime Module
In this page:
from datetime import datetime, timedelta
now = datetime.now()
now.strftime("format_code")
now + timedelta(days=n)Getting Current Date and Time
The datetime module models calendar dates and times as proper objects rather than raw numbers or strings, making date arithmetic and comparisons safe and readable.
datetime.now() returns a datetime object representing the current moment in your system's local time zone (naive, with no time zone attached unless you explicitly add one).
Example: Getting Current Date and Time
from datetime import datetime
now = datetime.now() # current local date and time
print(type(now))Formatting Dates with strftime
strftime() converts a datetime object into a custom-formatted string using format codes like %Y for a 4-digit year, %m for a zero-padded month, and %d for the day -- the mnemonic is 'string format time'.
This is how you control exactly what a date looks like when displaying it to users or writing it to a file.
Example: Formatting Dates with strftime
from datetime import datetime
d = datetime(2024, 3, 15)
print(d.strftime("%Y-%m-%d")) # formats the datetime as a custom stringParsing Strings with strptime
strptime() does the reverse: it parses a text string into a datetime object according to a format string you provide that must match the input's layout exactly.
This is essential when reading dates that arrive as plain text, from CSV files, web form submissions, or external APIs.
Example: Parsing Strings with strptime
from datetime import datetime
d = datetime.strptime("2024-03-15", "%Y-%m-%d") # parses text into a datetime using the given format
print(d.year, d.month, d.day)Calculating Time Differences
A timedelta object represents a span of time -- days, seconds, or microseconds -- rather than a specific point in time.
Adding or subtracting a timedelta from a datetime computes a new date shifted forward or backward, which is how you calculate things like 'the date 30 days from now.'
Example: Calculating Time Differences
from datetime import datetime, timedelta
d = datetime(2024, 1, 1)
future = d + timedelta(days=30) # shifts the date 30 days forward
print(future)Date and Time Objects
The module also provides standalone date and time classes for when you only care about the calendar date or the time of day in isolation, rather than a combined instant.
Using the narrower type documents your intent clearly -- a birthday needs only a date, not a full datetime with an arbitrary time attached.
Example: Date and Time Objects
from datetime import date, time
birthday = date(2000, 5, 20) # calendar date only
meeting = time(14, 30) # time of day only
print(birthday, meeting)- Using
strftimeandstrptimewith mismatched format codes, such as%mfor minutes, when%Mis minutes and%mis month. - Subtracting two dates and expecting a number, when the result is a
timedelta; use.daysor.total_seconds(). - Mixing timezone-aware and naive datetimes, which raises
TypeErrorwhen you compare or subtract them.
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