Days in month

ruby-talk
1

Is there a method of Date or Time that gives the number of days in a date's month or the last day of the month like:

d = Date.new(2005,4,20)
d.days_in_month #-> 30
#or
d.last_day_of_month #-> 30

Thanks,

Dan

2

Hi --

Is there a method of Date or Time that gives the number of days in a date's month or the last day of the month like:

d = Date.new(2005,4,20)
d.days_in_month #-> 30
#or
d.last_day_of_month #-> 30

Funny you should ask :slight_smile:

This came up on IRC a month or two ago, and the answer appears to be
no. So I wrote one:

# Date.dim -- days in month

require 'date'

class Date
   def dim
     d,m,y = mday,month,year
     d += 1 while Date.valid_civil?(y,m,d)
     d - 1
   end
end

if __FILE__ == $0
   puts (Date.today >> 1).dim
   puts (Date.today << 1).dim
   puts (Date.new(2004,2)).dim
end

__END__

David

···

On Tue, 26 Apr 2005, Dan Fitzpatrick wrote:

--
David A. Black
dblack@wobblini.net

3

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

d = Date.new(2005,4,20)
puts d.days_in_month #-> 30

4

from the excellent impl in the 'days of month' thread earlier this week:

   harp:~ > cat a.rb
   require 'date'

   class Date
     def days_in_month
       self::class.civil(year, month, -1).day
     end
     alias dim days_in_month
     def weekdays
       (1..dim).to_a
     end
   end

   p Date::new(2005, 02).weekdays
   p Date::new(2005, 12).weekdays

   harp:~ > ruby a.rb
   [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28]
   [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31]

   harp:~ > cal 2 2005
       February 2005
   Su Mo Tu We Th Fr Sa
          1 2 3 4 5
    6 7 8 9 10 11 12
   13 14 15 16 17 18 19
   20 21 22 23 24 25 26
   27 28

   harp:~ > cal 12 2005
       December 2005
   Su Mo Tu We Th Fr Sa
                1 2 3
    4 5 6 7 8 9 10
   11 12 13 14 15 16 17
   18 19 20 21 22 23 24
   25 26 27 28 29 30 31

boy i love ruby.

cheers.

-a

···

On Tue, 26 Apr 2005, Dan Fitzpatrick wrote:

Is there a method of Date or Time that gives the number of days in a date's
month or the last day of the month like:

d = Date.new(2005,4,20)
d.days_in_month #-> 30
#or
d.last_day_of_month #-> 30

--

email :: ara [dot] t [dot] howard [at] noaa [dot] gov
phone :: 303.497.6469
although gold dust is precious, when it gets in your eyes, it obstructs
your vision. --hsi-tang

===============================================================================

5

JC,

Thanks for the simple solution.

Dan

jc wrote:

···

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

d = Date.new(2005,4,20) puts d.days_in_month #-> 30

6

!!! Yowser!

7

Nice! Here's a slight variation that's even simpler:

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