ruby shortcut and format specifier

NOTE: Some of these seem only to work for DateTime (e.g. %L, %N)


%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
%C - Century (20 in 2009)
%d - Day of the month (01..31)
%D - Date (%m/%d/%y)
%e - Day of the month, blank-padded ( 1..31)
%F - Equivalent to %Y-%m-%d (the ISO 8601 date format)
%h - Equivalent to %b
%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)
%k - hour, 24-hour clock, blank-padded ( 0..23)
%l - hour, 12-hour clock, blank-padded ( 0..12)
%L - Millisecond of the second (000..999)
%m - Month of the year (01..12)
%M - Minute of the hour (00..59)
%n - Newline (n)
%N - Fractional seconds digits, default is 9 digits (nanosecond)

• %3N millisecond (3 digits)
  
• %6N microsecond (6 digits)
  
• %9N nanosecond (9 digits)
  

%p - Meridian indicator (“AM” or “PM”)
%P - Meridian indicator (“am” or “pm”)
%r - time, 12-hour (same as %I:%M:%S %p)
%R - time, 24-hour (%H:%M)
%s - Number of seconds since 1970-01-01 00:00:00 UTC.
%S - Second of the minute (00..60)
%t - Tab character (t)
%T - time, 24-hour (%H:%M:%S)
%u - Day of the week as a decimal, Monday being 1. (1..7)
%U - Week number of the current year, starting with the first Sunday as the first day of the first week (00..53)
%v - VMS date (%e-%b-%Y)
%V - Week number of year according to ISO 8601 (01..53)
%W - Week number of the current year, starting with the first Monday as the first day of the first 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 as hour offset from UTC (e.g. +0900)
%Z - Time zone name
%% - Literal “%” character

t = Time.now                        #=> 2007-11-19 08:37:48 -0600
t.strftime("Printed on %m/%d/%Y")   #=> "Printed on 11/19/2007"
t.strftime("at %I:%M%p")            #=> "at 08:37AM"