Ruby/Date/DateTime

require "date"
module Week
  def week
    (yday + 7 - wday) / 7
  end
end
class Date
  include Week
end
class Time
  include Week
end
saturday = DateTime.new(2005, 1, 1)
saturday.week                                    # => 0
(saturday+1).week                                # => 1   #Sunday, January 2
(saturday-1).week                                # => 52  #Friday, December 31

require "date"
now_time = Time.new
now_datetime = DateTime.now
puts now_time.year                       
puts now_datetime.year                   
puts now_time.hour                       
puts now_datetime.hour                   
puts now_time.zone                       
puts now_datetime.zone                   
puts now_time.isdst                      
puts now_time.usec                        # => 247930
# That is, 247930 microseconds
puts now_datetime.sec_fraction            # => Rational(62191, 21600000000)
# That is, about 287921 microseconds

require "date"
class Time
  def to_datetime
    seconds = sec + Rational(usec, 10**6)
    offset = Rational(utc_offset, 60 * 60 * 24)
    DateTime.new(year, month, day, hour, min, seconds, offset)
  end
end
puts time = Time.gm(2000, 6, 4, 10, 30, 22, 4010)
puts time.to_datetime.to_s

require "date"
eastern = DateTime.now
eastern.to_s
pacific_offset = Rational(-7, 24)
pacific = eastern.new_offset(pacific_offset)
pacific.to_s

require "date"
puts DateTime::new(1865, 4, 9).to_s            
puts DateTime::new(2100, 1, 1).to_s

require "date"
puts DateTime.civil(1999, 12, 31, 23, 21, Rational(51044, 100000)).to_s
 
puts DateTime.civil(1991, 10, 1).to_s
 
puts DateTime.civil(2000).to_s

require "date"
now = DateTime.now
now.to_s              
now.new_offset.to_s   
# The original object was not affected by the time zone conversion.
puts now.to_s

require "date"
puts DateTime.parse("02-09-2007 12:30:44 AM").to_s
puts DateTime.parse("02-09-2007 12:30:44 PM EST").to_s

date_and_time = "%m-%d-%Y %H:%M:%S %Z"
require "date"
 
puts DateTime.strptime("02-09-2007 12:30:44 EST", date_and_time).to_s
puts DateTime.strptime("02-09-2007 12:30:44 PST", date_and_time).to_s
puts DateTime.strptime("02-09-2007 12:30:44 GMT", date_and_time).to_s

require "date"
twelve_hour_clock_time = "%m-%d-%Y %I:%M:%S %p"
puts DateTime.strptime("02-09-2007 12:30:44 AM", twelve_hour_clock_time).to_s
puts DateTime.strptime("02-09-2007 12:30:44 PM", twelve_hour_clock_time).to_s

require "date"
local = DateTime.now
utc = local.new_offset
puts local.offset                  # => Rational(-5, 24)
puts local_from_utc = utc.new_offset(local.offset)
puts local_from_utc.to_s           # => "2006-03-18T20:15:58-0500"
puts local == local_from_utc       # => true

require "date"
local = DateTime.now
local.to_s                   # => "2006-03-18T20:15:58-0500"
utc = local.new_offset(0)
utc.to_s                     # => "2006-03-19T01:15:58Z"

my_offset = DateTime.now.offset                   # => Rational(-5, 24)
puts DateTime.civil(1999, 12, 31, 23, 21, Rational(51044, 100000), my_offset).to_s

require "date"
puts DateTime::now.to_s

require "date"
puts DateTime::new.to_s

require "date"
TRY_FORMATS = ["%d/%m/%y", "%Y %m %d"]
def try_to_parse(s)
  parsed = nil
  TRY_FORMATS.each do |format|
    begin
      parsed = Date.strptime(s, format)
      break
    rescue ArgumentError
    end
  end
  return parsed
end
puts try_to_parse("1/10/07").to_s            # => "2007-10-01"
puts try_to_parse("2007 1 10").to_s          # => "2007-01-10"