This Ruby code converts a string into a date and increments the day, week, month, quarter or year.

def date_add(sdate='', unit='',i=0)

  sdate[/(\d+)\/(\d+)\/(\d+)\s(\d+):(\d+):(\d+)/]
  iyear = $3.to_i; imonth = $2.to_i; iday = $1.to_i; ihour = $4.to_i; imin = $5.to_i; isec = $6.to_i
  
  case  unit
    when 'days'
      t1 = Time.local(iyear,imonth,iday,ihour,imin,isec)
      t1 += (60 * 60 * 24 * i)
    when 'weeks'
      t1 = Time.local(iyear,imonth,iday,ihour,imin,isec)
      t1 += (60 * 60 * 24 * 7 * i) 
    when 'months'
      imonth += i
      if imonth < 12 then
        t1 = Time.local(iyear,imonth+i,iday,ihour,imin,isec)
      else
        t1 = Time.local(iyear+=1,imonth -12,iday,ihour,imin,isec)
      end
    when 'quarter'
      imonth += 3
      if imonth <= 12 then
        t1 = Time.local(iyear,imonth,iday,ihour,imin,isec)
      else
        t1 = Time.local(iyear+=1,imonth - 12,iday,ihour,imin,isec)
      end    
    when 'years'
      t1 = Time.local(iyear+i,imonth,iday,ihour,imin,isec)
    else
      raise 'not a valid date unit'
  end
  t1
end

date_add("17/03/2008 17:48:00",'months',2)

output: Sat May 17 17:48:00 +0100 2008

This example creates a date and time variable which represents 22nd March 2008 4:30pm and 12 seconds.

d2 = DateTime.new(y=200,m=3,d=22, h=16,min=30,s=12)

or convert a date string into a DataTime object:

"17/03/2009 17:48:00"[/(\d+)\/(\d+)\/(\d+)\s(\d+):(\d+):(\d+)/]
d2 = DateTime.new(y=$3.to_i,m=$2.to_i,d=$1.to_i, h=$4.to_i,min=$5.to_i,s=$6.to_i)

or convert a date string into a Time object:

"22/03/2008 17:48:00"[/(\d+)\/(\d+)\/(\d+)\s(\d+):(\d+):(\d+)/]
iyear = $3.to_i; imonth = $2.to_i; iday = $1.to_i; ihour = $4.to_i; imin = $5.to_i; isec = $6.to_i
twork = Time.local(iyear,imonth,iday,ihour,imin,isec) 
puts 'we still have time to party' if Time.now < twork 

Reference:
Class: DateTime [ruby-doc.org]
Class: Time [ruby-doc.org]

This Ruby code selects file directories which are older than a certain date and outputs an XML file naming all the directories to be removed. It does this by reading a directory listing formatted within the XML file 'dir.xml', all directories are named by a date-stamp, which is used to determine if the directory should be removed.

This example is used to maintain the webcamera (named 'pear') which saves it's images to a date-stamped directory daily. Any directory which is older than 14 days will be marked for deletion.

  def directory_housekeeping()
    lifespan = 14
    format_mask = 'm_d_y'
    separator = format_mask.match(/[\_*\-]/).to_s
    
    earliest_date = Time.now + (60 * 60 * 24) * -lifespan
    cut_off_date = Date.new(y=earliest_date.year,m=earliest_date.month,d=earliest_date.day)
        
    a_format = Array.new
    a_format[0] = format_mask.match(/^[y,m,d]*/).to_s
    a_format[1] = format_mask.match(separator + '[y,m,d]*').to_s.gsub(separator,'')
    a_format[2] = format_mask.match('[y,m,d]$').to_s
    
    file = File.new('../housekeeping/webcam_pear/dir.xml')
    ddoc = REXML::Document.new(file)
    file.close
    
    file_delete = File.new('../housekeeping/webcam_pear/files2delete.xml', 'w')
    doc_delete = Document.new()
    doc_delete.add_element('files')
    
    ddoc.root.elements.each('file') do |file_node|
      sfile = file_node.text
      idate = Array.new
      idate[0] = sfile.match(/^\d*/).to_s.to_i
      idate[1] = sfile.match(/\_\d*/).to_s.gsub(separator,'').to_i
      idate[2] = sfile.match(/\_\d*\d$/).to_s.gsub(separator,'').to_i

      h = Hash.new
      0.upto(2) {|i| h[a_format[i]] = idate[i]}

      file_date = Date.new(y=h['y'], m=h['m'], d=h['d'])

      if file_date < cut_off_date
        o_file2delete = Element.new('file')
        o_file2delete.text = file_date.strftime(dformat)
        doc_delete.root.add_element o_file2delete
      end
    end
    file_delete.puts doc_delete
  end

file: dir.xml

<dir>
  <file>11_4_2007</file>
  <file>11_5_2007</file>
  <file>11_6_2007</file>
  <file>11_7_2007</file>
  <file>11_8_2007</file>
  <file>11_9_2007</file>
  <file>12_10_2007</file>
  <file>12_11_2007</file>
  <file>12_1_2007</file>
  <file>12_12_2007</file>
  <file>12_13_2007</file>
  <file>12_14_2007</file>
  <file>12_15_2007</file>
  <file>12_16_2007</file>
  <file>12_17_2007</file>
  <file>12_18_2007</file>
  <file>12_19_2007</file>
  <file>12_20_2007</file>
  <file>12_21_2007</file>
  <file>12_2_2007</file>
  <file>12_22_2007</file>
  <file>12_23_2007</file>
  <file>12_24_2007</file>
  <file>12_25_2007</file>
  <file>12_26_2007</file>
  <file>12_27_2007</file>
  <file>12_28_2007</file>
  <file>12_3_2007</file>
  <file>12_4_2007</file>
  <file>12_5_2007</file>
  <file>12_6_2007</file>
  <file>12_7_2007</file>
  <file>12_8_2007</file>
  <file>12_9_2007</file>
 </dir>

file: files2delete.xml

<files>
  <file>11_4_2007</file>
  <file>11_5_2007</file>
  <file>11_6_2007</file>
  <file>11_7_2007</file>
  <file>11_8_2007</file>
  <file>11_9_2007</file>
  <file>12_10_2007</file>
  <file>12_11_2007</file>
  <file>12_1_2007</file>
  <file>12_12_2007</file>
  <file>12_13_2007</file>
  <file>12_14_2007</file>
  <file>12_15_2007</file>
  <file>12_2_2007</file>
  <file>12_3_2007</file>
  <file>12_4_2007</file>
  <file>12_5_2007</file>
  <file>12_6_2007</file>
  <file>12_7_2007</file>
  <file>12_8_2007</file>
  <file>12_9_2007</file>
 </files>

This example creates a date variable which represents 22nd March 2008.

  require 'date'
  d1 = Date.new(y=2008,m=3,d=22)
  puts d1

output: 2008-03-22