Python Date Time String Format

Python Date Time String Format

Discussion of usage of strfttime and strptime functions in python to produce and consume Date time strings

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Introduction

Date and time are two of the most useful yet confusing things in programming life. Date time storage and retrieval required a common well-decided protocol. Timezone conversion is also one of the most challenging tasks. That's why while working with Date and Time, developers should be extra curious. When it comes to working with date and time, Python's datetime library is the most reliable one. The Datetime library tries to solve all the problems to a large extent. So that's why developers love to use it.

While creating a user-oriented application, one of the most common tasks is to create a well-formatted Date-time string. Example: Friday, 7 October 2022.

Another useful task is to convert the Date-time string into a datetime object so that we can use that object with the rest of the program.

Datetime object

Python's Datetime Object is an object which stores information on a particular date and time. It stores day, month, year, hour, minute, second, and timezone information as parameters. The object has various methods to do almost everything possible.

The scope of this blog is the formatting of the date-time object, but not the description of the object itself. So if you want to know more, I am adding some references.

Conversion of user-given String to Python's Datetime Object

Often time, when users give a date or time input, they often use the specified format by the app. Some common formats are DD/MM/YYYY, MM/DD/YYYY, and HH:MM:SS, like so. Now, it's the responsibility of the developer to convert the given string to a more useful object.

To convert user given string to a datetime object we use strptime.

strptime

from datetime import datetime

datetime.strptime(date_string, format_string) -> Datetime

Here, date_string is the input from the user, and format_string is the expected format, in which the user has given the date_string. The format_string has the format specifiers, which will be used to extract the values from the date_string.

Example:

from datetime import datetime

datetime.strptime("07/10/2022", "%d/%m/%Y")
# datetime.datetime(2022, 10, 7, 0, 0)

Explaination

The date_string (07/10/2022) is mapped with the format string (%d/%m/%Y).

Date string valueFormat string valueExplanation
07%d%d is the format specifier for Day, so 07 is considered as the day
//Ignored, as not a format specifier
10%m%m is the format specifier for Month, so 10 is considered as the Month
//Ignored, as not a format specifier
2022%Y%Y is the format specifier for Long Year, so 2022 is considered as the Year

See the Format list below.

Conversion Datetime Object to user-readable string

Now that, you have a new datetime object and you have done some operations with that, you need to properly format it to string so that users can understand it very well. So now our task is to convert the object to a string.

To convert a datetime object to a string, we use strftime.

strftime

# Method 1
datetime_object.strftime(format_string) -> formatted_string

# Method 2
from datetime import datetime
datetime.strftime(Datetime, format_string) -> formatted_string
  • In Method 1, we use strftime as a method call to the datetime object and pass the format_string as a parameter.

  • In Method 2, we are directly calling the strftime as a function and passing the datetime object as the first param, and format_string as the second param.

For both cases, it'll return a formatted date and time string.

Example:

from datetime import datetime

datetime.now().strftime("%d/%m/%Y")
# '07/10/2022' (current date in the above format)

Format Specifiers List

Below there are all format specifiers used while formatting. The format specifies are grouped by their types.

Weekday

DirectiveMeaningExample
%aAbbreviated weekday name.Sun, Mon, ...
%AFull weekday name.Sunday, Monday, ...
%wWeekday as a decimal number.0, 1, ..., 6
%WWeek number of the year (Monday as the first day of the week). All days in a new year preceding the first Monday are considered to be in week 0.00, 01, ..., 53
%UWeek number of the year (Sunday as the first day of the week). All days in a new year preceding the first Sunday are considered to be in week 0.00, 01, ..., 53

Day

DirectiveMeaningExample
%dDay of the month as a zero-padded decimal.01, 02, ..., 31
%-dDay of the month as a decimal number.1, 2, ..., 31
%jDay of the year as a zero-padded decimal number.001, 002, ..., 366
%-jDay of the year as a decimal number.1, 2, ..., 366

Month

DirectiveMeaningExample
%bAbbreviated month name.Jan, Feb, ..., Dec
%BFull month name.January, February, ...
%mMonth as a zero-padded decimal number.01, 02, ..., 12
%-mMonth as a decimal number.1, 2, ..., 12

Year

DirectiveMeaningExample
%yYear without century as a zero-padded decimal number.00, 01, ..., 99
%-yYear without century as a decimal number.0, 1, ..., 99
%YYear with century as a decimal number.2013, 2019 etc.

Hour

DirectiveMeaningExample
%HHour (24-hour clock) as a zero-padded decimal number.00, 01, ..., 23
%-HHour (24-hour clock) as a decimal number.0, 1, ..., 23
%IHour (12-hour clock) as a zero-padded decimal number.01, 02, ..., 12
%-IHour (12-hour clock) as a decimal number.1, 2, ... 12
%pLocale’s AM or PM.AM, PM

Minutes

DirectiveMeaningExample
%MMinute as a zero-padded decimal number.00, 01, ..., 59
%-MMinute as a decimal number.0, 1, ..., 59

Seconds

DirectiveMeaningExample
%SSecond as a zero-padded decimal number.00, 01, ..., 59
%-SSecond as a decimal number.0, 1, ..., 59
%fMicrosecond as a decimal number, zero-padded on the left.000000 - 999999

Time Zone

DirectiveMeaningExample
%zUTC offset in the form +HHMM or -HHMM.
%ZTime zone name.

Overall Representation

DirectiveMeaningExample
%cLocale’s appropriate date and time representation.Mon Sep 30 07:06:05 2013
%xLocale’s appropriate date representation.09/30/13
%XLocale’s appropriate time representation.07:06:05
%%A literal '%' character.%

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