How to get the number of days in a given month in Ruby, accounting for year?

Question

I\'m sure there\'s a good simple elegant one-liner in Ruby to give you the number of days in a given month, accounting for year, such as \"February 1997\". What is it?

Answer 1

I think it's the simplest way to get it

def get_number_of_days(date = Date.today)
  Date.new(date.year, date.month, -1).mday
end

Answer 2

A simple way using Date:

def days_of_month(month, year)
  Date.new(year, month, -1).day
end

Answer 3

In Rails project for current date

Time.days_in_month(Time.now.month, Time.now.year)

For any date t which is instance of Time

Time.days_in_month(t.month, t.year)

or

t.end_of_month.day

.
If you have UTC seconds, you need to get an instance of Time first

Time.at(seconds).end_of_month.day

Answer 4

How about:

require 'date'

def days_in_month(year, month)
  (Date.new(year, 12, 31) << (12-month)).day
end

# print number of days in Feburary 2009
puts days_in_month(2009, 2)

You may also want to look at Time::days_in_month in Ruby on Rails.

Answer 5

This is the implementation from ActiveSupport (a little adapted):

COMMON_YEAR_DAYS_IN_MONTH = [nil, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

def days_in_month(month, year = Time.now.year)
   return 29 if month == 2 && Date.gregorian_leap?(year)
   COMMON_YEAR_DAYS_IN_MONTH[month]
end

Answer 6

require 'date'

def days_in_month(year, month)
  Date.new(year, month, -1).day
end

# print number of days in February 2012
puts days_in_month(2012, 2)