Common Format Codes Reference Catalog

🏷️ Working with Dates and Time / Formatting and Parsing Dates

📚 All-in-One📖 Theory Only💻 Code Only

When working with dates and time in Python, you will often need to convert date objects into readable strings or parse strings back into date objects. The strftime (string format time) and strptime (string parse time) methods rely on a set of format codes that tell Python exactly how to interpret or display date and time components. This reference catalog covers the most commonly used format codes that you will encounter in everyday scripting and automation tasks.

⚙️ Year Format Codes

These codes control how the year portion of a date is displayed or parsed.

%Y – Full year with century (e.g., 2024, 1999)
%y – Two-digit year without century (e.g., 24, 99)
%G – ISO week-based year (used with week number codes)
%g – Two-digit ISO week-based year

📅 Month Format Codes

Use these to represent the month in numeric, abbreviated, or full text form.

%m – Month as a zero-padded number (e.g., 01 for January, 12 for December)
%b – Abbreviated month name (e.g., Jan, Feb, Dec)
%B – Full month name (e.g., January, December)

🗓️ Day Format Codes

These codes handle the day of the month and the day of the week.

%d – Day of the month as a zero-padded number (e.g., 01, 15, 31)
%j – Day of the year as a zero-padded number (e.g., 001 to 366)
%a – Abbreviated weekday name (e.g., Mon, Tue, Sun)
%A – Full weekday name (e.g., Monday, Tuesday)
%w – Weekday as a number (0 for Sunday, 6 for Saturday)
%u – Weekday as a number (1 for Monday, 7 for Sunday)

🕐 Time Format Codes

For representing hours, minutes, seconds, and time-related components.

%H – Hour in 24-hour format, zero-padded (e.g., 00 to 23)
%I – Hour in 12-hour format, zero-padded (e.g., 01 to 12)
%M – Minute as a zero-padded number (e.g., 00 to 59)
%S – Second as a zero-padded number (e.g., 00 to 59)
%f – Microsecond as a six-digit zero-padded number (e.g., 000000 to 999999)
%p – AM or PM designation (e.g., AM, PM)

🌍 Week and Timezone Codes

These codes are useful for ISO week numbering and timezone handling.

%W – Week number of the year (Monday as first day of week), zero-padded (e.g., 00 to 53)
%U – Week number of the year (Sunday as first day of week), zero-padded (e.g., 00 to 53)
%V – ISO week number (Monday as first day), zero-padded (e.g., 01 to 53)
%z – UTC offset in the form +HHMM or -HHMM (e.g., +0530, -0400)
%Z – Timezone name (e.g., UTC, EST, IST)

🛠️ Common Format Combinations

Here are some frequently used format patterns that combine multiple codes for practical use.

%Y-%m-%d – Standard date format (e.g., 2024-12-25)
%d/%m/%Y – Day-first date format (e.g., 25/12/2024)
%m/%d/%Y – Month-first date format (e.g., 12/25/2024)
%Y-%m-%d %H:%M:%S – Full datetime with 24-hour time (e.g., 2024-12-25 14:30:00)
%a, %d %b %Y %H:%M:%S %z – RFC 2822 style (e.g., Wed, 25 Dec 2024 14:30:00 +0000)
%I:%M:%S %p – 12-hour time with AM/PM (e.g., 02:30:00 PM)

📊 Quick Reference Comparison Table

Code	Meaning	Example Output
%Y	Full year	2024
%y	Two-digit year	24
%m	Zero-padded month	12
%b	Abbreviated month	Dec
%B	Full month name	December
%d	Zero-padded day	25
%a	Abbreviated weekday	Wed
%A	Full weekday	Wednesday
%H	24-hour hour	14
%I	12-hour hour	02
%M	Minute	30
%S	Second	00
%p	AM/PM	PM
%z	UTC offset	+0000
%Z	Timezone name	UTC

🕵️ Practical Usage Tips

Always match the format code case carefully. For example, %Y (full year) and %y (two-digit year) produce very different results.
When parsing strings with strptime, the format string must exactly match the structure of the input string, including any separators like dashes, slashes, or colons.
For 12-hour time formatting, always include %p to distinguish AM from PM, otherwise the output may be ambiguous.
The %f code for microseconds is most useful when working with high-precision timestamps or logging events that occur rapidly.
Timezone codes (%z and %Z) only work correctly if the datetime object has timezone information attached. Naive datetime objects will return empty strings for these codes.

🧪 Example Format Strings in Practice

To display a timestamp in a log file: %Y-%m-%d %H:%M:%S produces 2024-12-25 14:30:00
For a user-friendly date on a report: %B %d, %Y produces December 25, 2024
For parsing a common API date format: %Y-%m-%dT%H:%M:%S%z matches strings like 2024-12-25T14:30:00+0000
For a compact filename-friendly format: %Y%m%d_%H%M%S produces 20241225_143000

This catalog serves as a quick lookup reference whenever you need to format or parse date and time strings in Python. Bookmark this page and refer back to it as you build scripts that handle scheduling, logging, data processing, or any task involving temporal data.

This reference catalog lists the most common format codes used with strftime() and strptime() to convert between datetime objects and strings.

📅 Example 1: Year, Month, and Day Codes

Shows the three most common codes for extracting year, month, and day components.

from datetime import datetime

now = datetime(2024, 3, 15, 14, 30, 0)

year_full = now.strftime("%Y")
year_short = now.strftime("%y")
month_num = now.strftime("%m")
month_name_full = now.strftime("%B")
month_name_short = now.strftime("%b")
day_num = now.strftime("%d")
day_name_full = now.strftime("%A")
day_name_short = now.strftime("%a")

print(year_full)
print(year_short)
print(month_num)
print(month_name_full)
print(month_name_short)
print(day_num)
print(day_name_full)
print(day_name_short)

📤 Output: 2024
📤 Output: 24
📤 Output: 03
📤 Output: March
📤 Output: Mar
📤 Output: 15
📤 Output: Friday
📤 Output: Fri

⏰ Example 2: Time Component Codes

Demonstrates codes for hours, minutes, seconds, and AM/PM markers.

from datetime import datetime

now = datetime(2024, 3, 15, 14, 30, 45)

hour_24 = now.strftime("%H")
hour_12 = now.strftime("%I")
minute = now.strftime("%M")
second = now.strftime("%S")
am_pm = now.strftime("%p")

print(hour_24)
print(hour_12)
print(minute)
print(second)
print(am_pm)

📤 Output: 14
📤 Output: 02
📤 Output: 30
📤 Output: 45
📤 Output: PM

🗓️ Example 3: Combined Date and Time Format

Shows how to build a full timestamp string using multiple codes together.

from datetime import datetime

now = datetime(2024, 3, 15, 14, 30, 45)

full_date = now.strftime("%A, %B %d, %Y")
full_time = now.strftime("%I:%M:%S %p")
timestamp = now.strftime("%Y-%m-%d %H:%M:%S")

print(full_date)
print(full_time)
print(timestamp)

📤 Output: Friday, March 15, 2024
📤 Output: 02:30:45 PM
📤 Output: 2024-03-15 14:30:45

🔄 Example 4: Parsing a String into a Datetime Object

Shows how to use format codes in reverse with strptime() to read a date string.

from datetime import datetime

date_string = "2024-03-15 14:30:45"
date_format = "%Y-%m-%d %H:%M:%S"

parsed_date = datetime.strptime(date_string, date_format)

print(parsed_date)
print(parsed_date.year)
print(parsed_date.month)
print(parsed_date.day)

📤 Output: 2024-03-15 14:30:45
📤 Output: 2024
📤 Output: 3
📤 Output: 15

📋 Example 5: Common Date Formats for Engineers

Shows practical format strings engineers use for logs, reports, and filenames.

from datetime import datetime

now = datetime(2024, 3, 15, 14, 30, 45)

log_format = now.strftime("[%Y-%m-%d %H:%M:%S]")
file_format = now.strftime("report_%Y%m%d_%H%M%S")
iso_format = now.strftime("%Y-%m-%dT%H:%M:%S")
us_format = now.strftime("%m/%d/%Y")
eu_format = now.strftime("%d.%m.%Y")

print(log_format)
print(file_format)
print(iso_format)
print(us_format)
print(eu_format)

📤 Output: [2024-03-15 14:30:45]
📤 Output: report_20240315_143045
📤 Output: 2024-03-15T14:30:45
📤 Output: 03/15/2024
📤 Output: 15.03.2024

📊 Common Format Codes Quick Reference Table

Code	Description	Example Output
`%Y`	4-digit year	2024
`%y`	2-digit year	24
`%m`	Month as zero-padded number	03
`%B`	Full month name	March
`%b`	Abbreviated month name	Mar
`%d`	Day of month, zero-padded	15
`%A`	Full weekday name	Friday
`%a`	Abbreviated weekday name	Fri
`%H`	Hour (24-hour clock)	14
`%I`	Hour (12-hour clock)	02
`%M`	Minute, zero-padded	30
`%S`	Second, zero-padded	45
`%p`	AM or PM	PM