Ruby Academy · Lesson

Parsing and Formatting

strftime and strptime.

Parsing and Formatting is a free Ruby Academy lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Ruby Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Formatting with strftime

strftime turns a Time or Date into a formatted string using format directives that start with %.

t = Time.new(2026, 5, 30, 14, 5, 9)
puts(t.strftime('%Y-%m-%d'))
puts(t.strftime('%H:%M:%S'))

Common Date Directives

Useful date directives:

%Y 4-digit year, %y 2-digit
%m month number, %B full month name
%d day of month, %j day of year

t = Time.new(2026, 5, 30)
puts(t.strftime('%B %d, %Y'))
puts(t.strftime('%y/%m/%d'))

Common Time Directives

Useful clock directives:

%H 24-hour, %I 12-hour
%M minutes, %S seconds
%p AM/PM

t = Time.new(2026, 5, 30, 14, 30)
puts(t.strftime('%I:%M %p'))
puts(t.strftime('%H:%M'))

Weekday and Names

%A is the full weekday name, %a abbreviated. %b is the abbreviated month name.

t = Time.new(2026, 5, 30)
puts(t.strftime('%A'))
puts(t.strftime('%a %b %d'))

Padding and Flags

Insert flags between % and the directive: - removes padding, 0 pads with zeros, _ pads with spaces.

t = Time.new(2026, 5, 5, 9, 0)
puts(t.strftime('%-d/%-m'))
puts(t.strftime('%H:%M'))

ISO 8601 Output

For interoperable timestamps, use iso8601 or the %FT%T%z pattern. ISO 8601 is the standard for APIs.

require 'time'
t = Time.new(2026, 5, 30, 14, 0, 0, '+00:00')
puts(t.utc.iso8601)

Parsing with Date.parse

Date.parse reads many common date string formats and guesses the layout. Convenient but lenient.

require 'date'
puts(Date.parse('2026-05-30'))
puts(Date.parse('30 May 2026'))

Parsing with Time.parse

Require time to add Time.parse, which reads full timestamps including the clock.

require 'time'
t = Time.parse('2026-05-30 14:30:00')
puts(t.hour)
puts(t.min)

Strict Parsing with strptime

When you know the exact format, use strptime. It uses the same directives as strftime and fails on mismatched input, which is safer.

require 'date'
d = Date.strptime('30/05/2026', '%d/%m/%Y')
puts(d.year)
puts(d.month)

strptime for Times

Time.strptime parses a timestamp with a known format into a Time.

require 'time'
t = Time.strptime('2026-05-30 14:05', '%Y-%m-%d %H:%M')
puts(t.hour)
puts(t.min)

parse vs strptime

Rule of thumb:

Use parse for flexible, human-entered text
Use strptime when the format is fixed and you want to reject anything else

require 'date'
puts(Date.parse('May 30 2026').iso8601)
puts(Date.strptime('2026-05-30', '%Y-%m-%d').iso8601)

Quick Check

Which directive produces a zero-padded 24-hour value in strftime?

Recap: Parsing and Formatting

You can convert between strings and dates both ways:

strftime formats with % directives
%Y %m %d %H %M %S %A %B and flags
parse is flexible, strptime is strict
Use iso8601 for API-friendly output

require 'date'
puts(Date.strptime('2026-05-30', '%Y-%m-%d').strftime('%A, %B %-d'))

Frequently asked questions

Is the “Parsing and Formatting” lesson free?

Yes — the full text of “Parsing and Formatting” is free to read here on the web, and the Ruby Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Ruby Academy course, upgrade to CoddyKit PRO.

What will I learn in “Parsing and Formatting”?

strftime and strptime. You practise Ruby Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Ruby Academy?

No prior experience is required. Ruby Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Parsing and Formatting” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Ruby Academy lesson?

Yes. Every Ruby Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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