CTIME Formatting Guide

Complete guide to CTIME timestamp formatting with 30+ directives, examples, and real-world use cases for logs, APIs, emails, and databases.

Overview

CTIME formatting provides a way to format timestamps using directives similar to the Unix strftime function. This guide explains how to use CTIME format strings with practical examples.

Basic Concept

CTIME formatting works by replacing format directives (special character sequences starting with %) with their corresponding components from a date/time value. For example:

• %Y represents the full 4-digit year

• %m represents the month (zero-padded)

• %d represents the day of month (zero-padded)

Common Timestamp Format Examples

ISO 8601 Format

Format:  %F %T
Example: 2025-12-23 14:30:45

Equivalent to: %Y-%m-%d %H:%M:%S

US Short Date Format

Format:  %m/%d/%y
Example: 12/23/25

Same as the %D or %x directive

Full Date and Time

Format:  %c
Example: Mon Dec 23 14:30:45 2025

Complete date and time representation

12-Hour Time with AM/PM

Format:  %I:%M:%S %p
Example: 02:30:45 PM

24-Hour Time Only

Format:  %R
Example: 14:30

Equivalent to: %H:%M

For 24-hour time with seconds:

Format:  %T
Example: 14:30:45

Equivalent to: %H:%M:%S

RFC 2822 Style

Format:  %a, %b %d %Y %H:%M:%S %z
Example: Mon, Dec 23 2025 14:30:45 -0700

Log Timestamp Format

Format:  %Y-%m-%d %H:%M:%S.%L
Example: 2025-12-23 14:30:45.999

Verbose Format

Format:  %A, %B %d, %Y at %I:%M %p
Example: Monday, December 23, 2025 at 02:30 PM

Directive Reference

Year

Directive	Description	Example
%Y	Year, zero-padded (0001-9999)	2025
%y	Year, last two digits	25

Month

Directive	Description	Example
%m	Month as decimal (01-12)	12
%o	Month space-padded (1-12)	12
%q	Month unpadded (1-12)	12
%B	Full month name	December
%b, %h	Abbreviated month	Dec

Day of Month

Directive	Description	Example
%d	Day zero-padded (01-31)	23
%e	Day space-padded (1-31)	23
%g	Day unpadded (1-31)	23

Weekday

Directive	Description	Example
%A	Full weekday name	Monday
%a	Abbreviated weekday	Mon

Hour (24-hour clock)

Directive	Description	Example
%H	Hour zero-padded (00-23)	14

Hour (12-hour clock)

Directive	Description	Example
%I	Hour zero-padded (01-12)	02
%l	Hour unpadded (0-12)	2
%p	Locale AM/PM	PM
%P	Locale am/pm	pm

Minute

Directive	Description	Example
%M	Minute zero-padded (00-59)	30

Second

Directive	Description	Example
%S	Second zero-padded (00-59)	45

Fractional Seconds

Directive	Description	Example
%L	Millisecond (000-999)	500
%f	Microsecond (000000-999999)	500000
%s	Nanosecond (000000000-999999999)	500000000

Timezone

Directive	Description	Example
%Z	Timezone name/abbreviation	MST
%z	UTC offset (±HHMM[SS[.ffffff]])	-0700
%w	UTC offset with seconds	-070000
%i	UTC offset (short form)	-07
%j	UTC offset with colons	-07:00
%k	UTC offset full format	-07:00:00

Composite Formats

Directive	Description	Equivalent
%D, %x	Short date (MM/DD/YY)	%m/%d/%y
%F	ISO 8601 date (YYYY-MM-DD)	%Y-%m-%d
%T, %X	ISO 8601 time (HH:MM:SS)	%H:%M:%S
%R	24-hour time (HH:MM)	%H:%M
%r	12-hour time with AM/PM	HH:MM:SS am/pm
%c	Full date and time	Mon Jan 02 15:04:05 2006

Special Characters

Directive	Description
%n	Newline character
%t	Horizontal tab character
%%	Literal % sign

Practical Usage Tips

1. Combining Directives: You can mix multiple directives in a single format string

   %Y-%m-%d %H:%M:%S   →   2025-12-23 14:30:45

2. Padding Variations: Different directives provide different padding options for the same component

   %m  →  12 (zero-padded)
   %o  →  12 (space-padded)
   %q  →  12 (unpadded)

3. Timezone Information: Include timezone data for complete timestamp information

   %Y-%m-%d %H:%M:%S %Z   →   2025-12-23 14:30:45 MST

4. Readable Formats: Use full month and weekday names for human-readable timestamps

   %A, %B %d %Y   →   Monday, December 23 2025

5. Millisecond Precision: Include %L for application logs

   %Y-%m-%d %H:%M:%S.%L   →   2025-12-23 14:30:45.500

Example Use Cases

Server Log Entry

[%Y-%m-%d %H:%M:%S.%L] User login: admin
→ [2025-12-23 14:30:45.500] User login: admin

API Response Timestamp

{
  "timestamp": "%FT%T%z",
  "event": "order_placed"
}
→ "timestamp": "2025-12-23T14:30:45-0700"

Email Header Format

Date: %a, %d %b %Y %H:%M:%S %z
→ Date: Mon, 23 Dec 2025 14:30:45 -0700

Database Audit Log

%Y-%m-%d %H:%M:%S | %A | Action: UPDATE
→ 2025-12-23 14:30:45 | Monday | Action: UPDATE

User-Friendly Display

"Last updated: %A at %I:%M %p"
→ "Last updated: Monday at 02:30 PM"