Ruby/Time/strftime

time = Time.gm(2005, 12, 31, 13, 22, 33)
word_date = "%A, %B %d, %Y"
time.strftime(word_date)                   # => "Saturday, December 31, 2005"

time = Time.gm(2005, 12, 31, 13, 22, 33)
american_date = "%D"
time.strftime(american_date)               # => "12/31/05"

time = Time.gm(2005, 12, 31, 13, 22, 33)
european_date = "%d/%m/%y"
time.strftime(european_date)               # => "31/12/05"

time = Time.gm(2005, 12, 31, 13, 22, 33)
four_digit_year_date = "%m/%d/%Y"
time.strftime(four_digit_year_date)        # => "12/31/2005"

time = Time.gm(2005, 12, 31, 13, 22, 33)
date_and_time = "%m-%d-%Y %H:%M:%S %Z"
time.strftime(date_and_time)               # => "12-31-2005 13:22:33 GMT"

time = Time.gm(2005, 12, 31, 13, 22, 33)
twelve_hour_clock_time = "%m-%d-%Y %I:%M:%S %p"
time.strftime(twelve_hour_clock_time)      # => "12-31-2005 01:22:33 PM"

require "date"
t1 = Time.local(2002,5,1)
d1 = Date.new(2002,5,1)
week1a = t1.strftime("%U").to_i   # 17
week1b = t1.strftime("%W").to_i   # 17
week1c = d1.cweek                 # 18
t2 = Time.local(2005,5,1)
d2 = Date.new(2005,5,1)
week2a = t2.strftime("%U").to_i   # 18
week2b = t2.strftime("%W").to_i   # 18
week2c = d2.cweek                 # 17

puts Time.gm(2006).strftime("The year is %Y!")   # => "The year is 2006!"

Format Meaning 
%a      The abbreviated weekday name ("Sun")
%A      The full weekday name ("Sunday")
%b      The abbreviated month name ("Jan")
%B      The full month name ("January")
%c      The preferred local date and time representation
%d      Day of the month (01..31)
%H      Hour of the day, 24 hour clock (00..23)
%I      Hour of the day, 12 hour clock (01..12)
%j      Day of the year (001..366)
%m      Month of the year (01..12)
%M      Minute of the hour (00..59)
%p      Meridian indicator ("AM" or "PM")
%S      Second of the minute (00..60)
%U      Week number of the current year, starting with thefirst Sunday as the first day of thefirst week (00..53)
%W      Week number of the current year, starting with thefirst Monday as the first day of thefirst week (00..53)
%w      Day of the week (Sunday is 0,0..6)
%x      Preferred representation for the date alone, no time
%X      Preferred representation for the time alone, no date
%y      Year without a century (00..99)
%Y      Year with century
%Z      Time zone name
%%      Literal % character