Date and Time

Ruby has three classes for working with moments in time:

Time is built in and represents a point in time (date plus time of day).
Date represents a calendar date without a time.
DateTime combines both and is nowadays rarely needed.

Time is available out of the box. For Date you need to add require 'date' at the top of your program or your irb session.

Time.now

Time.now returns the current moment:

$ irb
>> Time.now
=> 2026-04-19 14:23:11 +0200
>> Time.now.class
=> Time
>> exit

You can ask a Time object for its parts:

$ irb
>> t = Time.now
=> 2026-04-19 14:23:11 +0200
>> t.year
=> 2026
>> t.month
=> 4
>> t.day
=> 19
>> t.hour
=> 14
>> t.min
=> 23
>> t.sec
=> 11
>> t.wday
=> 0
>> exit

wday is the day of the week as a number, Sunday being 0.

Date.today

For calendar work without a time of day, use Date:

$ irb
>> require 'date'
=> true
>> Date.today
=> #<Date: 2026-04-19>
>> Date.today.class
=> Date
>> Date.new(2026, 12, 24)
=> #<Date: 2026-12-24>
>> exit

Arithmetic

Time arithmetic works in seconds:

$ irb
>> now = Time.now
=> 2026-04-19 14:23:11 +0200
>> now + 60
=> 2026-04-19 14:24:11 +0200
>> now + 3600
=> 2026-04-19 15:23:11 +0200
>> now - 86400
=> 2026-04-18 14:23:11 +0200
>> exit

So + 60 moves one minute forward, + 3600 one hour, + 86400 one day.

Subtracting two Time values gives you the gap between them in seconds:

$ irb
>> start_time = Time.now
=> 2026-04-19 14:23:11 +0200
>> 3.times { 1_000_000.times { } }
=> 3
>> elapsed = Time.now - start_time
=> 0.142857
>> exit

Date arithmetic works in days:

$ irb
>> require 'date'
=> true
>> today = Date.today
=> #<Date: 2026-04-19>
>> today + 7
=> #<Date: 2026-04-26>
>> today - 30
=> #<Date: 2026-03-20>
>> (Date.new(2026, 12, 25) - today).to_i
=> 250
>> exit

That last line answers "how many days until Christmas?".

Formatting with strftime

Time.now and Date.today print in Ruby’s default format. Real applications usually need a specific layout. strftime ("string format time") turns a Time or Date into a formatted string. You give it a template with placeholders:

%Y

four digit year (2026)

%m

month, zero padded (04)

%d

day of month, zero padded (19)

%H

hour, 24-hour, zero padded (14)

%M

minute, zero padded (23)

%S

second, zero padded (11)

%A

weekday name (Sunday)

%B

month name (April)

$ irb
>> t = Time.now
=> 2026-04-19 14:23:11 +0200
>> t.strftime('%Y-%m-%d')
=> "2026-04-19"
>> t.strftime('%d.%m.%Y')
=> "19.04.2026"
>> t.strftime('%H:%M')
=> "14:23"
>> t.strftime('%A, %B %d, %Y')
=> "Sunday, April 19, 2026"
>> exit

The same placeholders work on Date objects.

Parsing Strings into Dates

Going the other way, from a string to a Date, use Date.parse:

$ irb
>> require 'date'
=> true
>> Date.parse('2026-04-19')
=> #<Date: 2026-04-19>
>> Date.parse('19.04.2026')
=> #<Date: 2026-04-19>
>> Date.parse('April 19, 2026')
=> #<Date: 2026-04-19>
>> exit

Date.parse is forgiving but also a little magical, so for untrusted input it is safer to spell out the format with Date.strptime:

$ irb
>> require 'date'
=> true
>> Date.strptime('19.04.2026', '%d.%m.%Y')
=> #<Date: 2026-04-19>
>> exit

Time has the same pair: Time.parse (needs require 'time') and Time.strptime.

In a Rails application you get even nicer helpers: 1.day, 3.hours.ago, 2.weeks.from_now, Date.current. Those come from ActiveSupport, not from plain Ruby. Everything on this page works without Rails.