Python time.strftime Function

Last modified April 11, 2025

This comprehensive guide explores Python’s time.strftime function, which formats time tuples into readable strings. We’ll cover format codes, common patterns, and practical formatting examples.

Basic Definitions

The time.strftime function converts a time tuple or struct_time to a string according to format specifications. It’s the inverse of strptime.

Key characteristics: locale-aware formatting, supports numerous format codes, and works with time.struct_time objects. The function returns a string based on the format specification.

Basic Time Formatting

This example demonstrates basic usage of strftime to format the current time into different string representations.

basic_formatting.py

import time

Get current time as struct_time

current_time = time.localtime()

Format using strftime

print(time.strftime("%Y-%m-%d", current_time)) # 2025-04-11 print(time.strftime("%A, %B %d %Y", current_time)) # Friday, April 11 2025 print(time.strftime("%I:%M:%S %p", current_time)) # 02:30:45 PM print(time.strftime("%H:%M:%S", current_time)) # 14:30:45

This shows common format codes: %Y for year, %m for month, %d for day, %H for 24-hour, %I for 12-hour, %M for minutes, %S for seconds.

The function uses the current locale settings for month/day names and AM/PM indicators unless overridden.

Custom Date Formats

strftime allows creating custom date formats by combining format codes. This example shows various date formatting options.

custom_formats.py

import time

now = time.localtime()

Different date formats

print(time.strftime("%d/%m/%Y", now)) # 11/04/2025 (European style) print(time.strftime("%m-%d-%y", now)) # 04-11-25 (US short style) print(time.strftime("%Y%m%d", now)) # 20250411 (ISO compact) print(time.strftime("%A %d %B, %Y", now)) # Friday 11 April, 2025 print(time.strftime("%Y-%j", now)) # 2025-101 (year and day of year)

The %j format code shows day of year (1-366). %A and %B give full weekday and month names respectively.

Different regions prefer different date formats - strftime makes it easy to adapt to local conventions.

Time Formatting Options

This example focuses specifically on time formatting with various precision and representation options.

time_formats.py

import time

now = time.localtime()

Time formatting examples

print(time.strftime("%H:%M", now)) # 14:30 (24-hour with minutes) print(time.strftime("%I:%M:%S %p", now)) # 02:30:45 PM (12-hour with AM/PM) print(time.strftime("%H:%M:%S.%f", now)) # 14:30:45.123456 (with microseconds) print(time.strftime("%X", now)) # 14:30:45 (locale’s time representation)

Note that %f for microseconds may not work on all platforms as struct_time doesn’t store microseconds. The %X code uses locale-specific time format.

For precise time measurements, consider datetime which natively supports microseconds.

Locale-Aware Formatting

strftime respects locale settings for month/day names and other locale-specific representations. This example demonstrates this.

locale_formatting.py

import time import locale

now = time.localtime()

Default locale

print(time.strftime("%A, %B %d", now)) # Friday, April 11

Change to German locale

locale.setlocale(locale.LC_TIME, ‘de_DE’) print(time.strftime("%A, %B %d", now)) # Freitag, April 11

Change to French locale

locale.setlocale(locale.LC_TIME, ‘fr_FR’) print(time.strftime("%A, %B %d", now)) # vendredi, avril 11

Locale settings affect weekday names (%A), month names (%B), AM/PM (%p), and other textual representations.

Remember to handle potential locale availability issues in production code.

Combining Date and Time

This example shows how to create comprehensive datetime strings by combining date and time format codes.

datetime_formatting.py

import time

now = time.localtime()

Common combined formats

print(time.strftime("%c", now)) # Fri Apr 11 14:30:45 2025 (locale’s default) print(time.strftime("%Y-%m-%d %H:%M:%S", now)) # 2025-04-11 14:30:45 print(time.strftime("%a %b %d %H:%M:%S %Y", now)) # Fri Apr 11 14:30:45 2025 print(time.strftime("%A, %B %d %Y at %I:%M %p", now)) # Friday, April 11 2025 at 02:30 PM

The %c format code provides the locale’s appropriate date and time representation. Other combinations offer precise control over output.

For ISO 8601 format, consider using datetime.isoformat() instead.

Special Format Codes

strftime includes several special format codes for less common but useful representations. This example demonstrates them.

special_codes.py

import time

now = time.localtime()

Special format codes

print(time.strftime("%U", now)) # 15 (week number, Sunday first) print(time.strftime("%W", now)) # 15 (week number, Monday first) print(time.strftime("%w", now)) # 5 (weekday as decimal, 0=Sunday) print(time.strftime("%j", now)) # 101 (day of year) print(time.strftime("%Z", now)) # EDT (timezone name) print(time.strftime("%z", now)) # -0400 (UTC offset)

Week number calculations (%U, %W) vary by locale. Timezone information (%Z, %z) depends on platform support.

These codes are useful for specialized date calculations and timezone-aware applications.

Formatting UTC Time

This example shows how to format UTC time rather than local time using time.gmtime instead of time.localtime.

utc_formatting.py

import time

Get UTC time

utc_time = time.gmtime()

Format UTC time

print(time.strftime("%Y-%m-%d %H:%M:%S UTC", utc_time)) # 2025-04-11 18:30:45 UTC print(time.strftime("%H:%M Z", utc_time)) # 18:30 Z (Zulu time) print(time.strftime("%a, %d %b %Y %H:%M:%S GMT", utc_time)) # Fri, 11 Apr 2025 18:30:45 GMT

UTC formatting is essential for systems that need timezone-independent timestamps or for network protocols.

The ‘Z’ suffix indicates Zulu time (UTC+0), common in aviation and military.

Best Practices

• Locale awareness: Be mindful of locale settings for production code

• Error handling: Catch potential ValueError for invalid struct_time

• Readability: Use descriptive format strings for maintainability

• Performance: Reuse format strings for repeated formatting

• Timezones: Clearly indicate timezone in formatted output

Source References

• Python time.strftime Documentation

• Python strptime Documentation

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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