From: 7stud -- <bbxx789_05ss@...>
Date: 2011-05-01T04:41:43+09:00
Subject: Re: question about working with dates

eggman2001 wrote in post #995956:
> I have a list (in database) of weekday non-holiday dates that goes
> from present back to 1990. From this list, I'd like to pull out dates
> given different kinds of criteria and add them to an array. Examples
> of criteria are:
> - first day of the month for the most recent 5 years. Perhaps obvious,
> but the first weekday non-holiday of the month isn't necessarily day 1
> (i.e. 5/1).
>

All it takes is a little math:


require 'date'

#Create array of all weekday dates for last five years
#(probably faster than pulling them out of a database):

date_arr = []
previous_years = 5

1.upto(previous_years * 365) do |i|
  new_date = today - i

  next if [6,0].include?(new_date.wday)
  date_arr << new_date
end


#Print out the first weekday of each month:

date_arr.each do |date|
  year = date.year
  month = date.month
  first_day_of_month = Date.new(year, month, 1)

  while [6,0].include?(first_day_of_month.wday)
    first_day_of_month += 1
  end

  if date == first_day_of_month
    puts date
  end
end

--output:--
2011-04-01
2011-03-01
2011-02-01
2011-01-03
2010-12-01
2010-11-01
2010-10-01
2010-09-01
2010-08-02
2010-07-01
2010-06-01
2010-05-03
2010-04-01
2010-03-01
2010-02-01
2010-01-01
2009-12-01
2009-11-02
2009-10-01
2009-09-01
2009-08-03
2009-07-01
2009-06-01
2009-05-01
2009-04-01
2009-03-02
2009-02-02
2009-01-01
2008-12-01
2008-11-03
2008-10-01
2008-09-01
2008-08-01
2008-07-01
2008-06-02
2008-05-01
2008-04-01
2008-03-03
2008-02-01
2008-01-01
2007-12-03
2007-11-01
2007-10-01
2007-09-03
2007-08-01
2007-07-02
2007-06-01
2007-05-01
2007-04-02
2007-03-01
2007-02-01
2007-01-01
2006-12-01
2006-11-01
2006-10-02
2006-09-01
2006-08-01
2006-07-03
2006-06-01
2006-05-01

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