Ruby makes working with dates and times pleasantly straightforward once you know which class to reach for:
Date(calendar dates, no time of day)Time(time of day + timezone/offset, great for “now” and timestamps)DateTime(date + time + offset, more “calendar-like” thanTime)
You’ll use these built-ins most of the time:
require "date" # needed for Date and DateTime
1) Getting the Current Date and Time
Current time (Time)
now = Time.now
puts now
# => 2025-12-12 10:15:30 +0000 (example)
Current date (Date)
today = Date.today
puts today
# => 2025-12-12 (example)
Current date & time (DateTime)
dt = DateTime.now
puts dt
# => 2025-12-12T10:15:30+00:00 (example)
2) Creating Specific Dates and Times
Create a Date
d = Date.new(2025, 12, 25)
puts d
# => 2025-12-25
Parse a date string
d1 = Date.parse("2025-12-25")
d2 = Date.strptime("25/12/2025", "%d/%m/%Y")
puts d1
puts d2
# => 2025-12-25
# => 2025-12-25
Create a Time
t = Time.new(2025, 12, 25, 14, 30, 0, "+00:00")
puts t
# => 2025-12-25 14:30:00 +0000
Parse a Time (ISO 8601)
require "time"
t = Time.iso8601("2025-12-25T14:30:00+00:00")
puts t
# => 2025-12-25 14:30:00 +0000
3) Formatting Dates and Times
Date#strftime
d = Date.new(2025, 12, 25)
puts d.strftime("%A, %d %B %Y")
# => Thursday, 25 December 2025
Time#strftime
t = Time.new(2025, 12, 25, 14, 30, 0, "+00:00")
puts t.strftime("%Y-%m-%d %H:%M:%S %z")
# => 2025-12-25 14:30:00 +0000
Common format tokens:
%Yyear,%mmonth,%dday%Hhour (24h),%Mminute,%Ssecond%ztimezone offset,%Aweekday name,%Bmonth name
4) Date/Time Arithmetic (Add/Subtract)
Add days to a Date
d = Date.new(2025, 12, 25)
puts d + 7
# => 2026-01-01
Subtract dates (difference in days)
a = Date.new(2025, 12, 25)
b = Date.new(2025, 12, 12)
puts (a - b).to_i
# => 13
Add seconds/minutes/hours to a Time
t = Time.now
puts t + 60 # +1 minute
puts t + 3600 # +1 hour
puts t - 86400 # -1 day
5) Comparing Dates and Times
a = Date.new(2025, 12, 25)
b = Date.new(2025, 12, 12)
puts a > b # true
puts a == b # false
For Time:
t1 = Time.now
sleep 1
t2 = Time.now
puts t2 > t1 # true
6) Converting Between Date, Time, and DateTime
Date → Time (start of day, local)
d = Date.new(2025, 12, 25)
t = d.to_time
puts t
Time → Date
t = Time.now
puts t.to_date
Time → DateTime
require "date"
t = Time.now
puts t.to_datetime
Tip: conversions can be affected by timezone/offset and your environment.
7) Working With Timezones (Practical Basics)
Ruby’s built-in Time stores an offset (like +00:00) and can show local vs UTC.
UTC vs local
t = Time.now
puts t
puts t.utc
Force a specific offset
t = Time.new(2025, 12, 25, 14, 30, 0, "+02:00")
puts t
# => 2025-12-25 14:30:00 +0200
If you need full IANA timezone support (e.g., Europe/London) in plain Ruby, people often use tzinfo or Rails’ ActiveSupport::TimeZone.
8) Common Real-World Tasks
8.1) Validate a date string safely
require "date"
def valid_date?(str, fmt = "%Y-%m-%d")
Date.strptime(str, fmt)
true
rescue ArgumentError
false
end
puts valid_date?("2025-12-25") # true
puts valid_date?("2025-13-25") # false
8.2) Measure elapsed time (benchmark style)
start = Time.now
# ... code you want to measure ...
sleep 0.3
elapsed = Time.now - start
puts "Elapsed: #{elapsed.round(3)}s"
8.3) “Start of day” and “end of day” (without Rails)
require "date"
d = Date.today
start_of_day = Time.new(d.year, d.month, d.day, 0, 0, 0, "+00:00")
end_of_day = Time.new(d.year, d.month, d.day, 23, 59, 59, "+00:00")
puts start_of_day
puts end_of_day
FAQ
Q: What’s the difference between Date and Time in Ruby? A: Date represents calendar dates without time-of-day. Time includes time-of-day and timezone/offset, and is best for timestamps and “now”.
Q: How do I format a date in Ruby? A: Use strftime, e.g. Date.today.strftime("%Y-%m-%d").
Q: How do I parse a date safely in Ruby? A: Use Date.strptime inside a begin/rescue (or helper method) to handle invalid inputs.
Q: How do I add days to a date in Ruby? A: Date.new(2025,12,25) + 7 returns a new Date 7 days later.