diff --git a/lib/validates_timeliness/formats.rb b/lib/validates_timeliness/formats.rb
index 46a299d..2b46271 100644
--- a/lib/validates_timeliness/formats.rb
+++ b/lib/validates_timeliness/formats.rb
@@ -9,6 +9,9 @@ module ValidatesTimeliness
     mattr_accessor :valid_date_expressions
     mattr_accessor :valid_datetime_expressions
     
+    mattr_accessor :format_tokens
+    mattr_accessor :format_proc_args
+    
     # Format tokens:
     #   
     #      y = year
@@ -17,9 +20,11 @@ module ValidatesTimeliness
     #      h = hour
     #      n = minute
     #      s = second
-    #      u = micro-second
-    #   ampm = meridian (am or pm) with or without dots (eg, am, a.m, or a.m.)
+    #      u = micro-seconds
+    #   ampm = meridian (am or pm) with or without dots (e.g. am, a.m, or a.m.)
     #      _ = optional space
+    #     tz = Timezone abrreviation (e.g. UTC, GMT, PST, EST)
+    #     zo = Timezone offset (e.g. +10:00, -08:00)
     #
     #   All other characters are considered literal. You can embed regexp in the
     #   format but no gurantees that it will remain intact. If you avoid the use
@@ -32,6 +37,8 @@ module ValidatesTimeliness
     #   yyyyy = exactly 4 digit year
     #   mmm   = month long name (e.g. 'Jul' or 'July')
     #
+    #   u     = Special case which matches 1 to 3 digits
+    #
     #   Any other combination of repeating tokens will be swallowed up by the next
     #   lowest length valid repeating token (e.g. yyy will be replaced with yy)
     
@@ -57,7 +64,7 @@ module ValidatesTimeliness
       'd/m/yyyy',
       'd-m-yyyy',
       'd.m.yyyy',
-      'm/d/yy',      
+      'm/d/yy',
       'd/m/yy',
       'd-m-yy',
       'd.m.yy',
@@ -66,32 +73,72 @@ module ValidatesTimeliness
     ]
     
     @@valid_datetime_formats = [
+      'dd/mm/yyyy hh:nn:ss',
+      'dd/mm/yyyy hh:nn',
       'yyyy-mm-dd hh:nn:ss',
       'yyyy-mm-dd hh:nn',
-      'yyyy-mm-ddThh:nn:ss(?:Z|([-+]\d{2}:\d{2}))'
+      'yyyy-mm-ddThh:nn:ss(?:Z|zo)' # iso 8601
     ]
-     
-    def self.format_regexp_generator(string_format)
-      regexp = string_format.dup
+    
+    
+    # All tokens available for format construction. The token
+    # array is made of token regexp, validation regexp and key for
+    # format proc mapping if any. If the token needs no format
+    # proc arg then the validation regexp should not have a capturing
+    # group, as all captured groups are passed to the format proc.
+    @@format_tokens = [
+      { 'mmm'  => [ /m{3,}/, '(\w{3,9})', :month ] },
+      { 'mm'   => [ /m{2}/,  '(\d{2})',   :month ] },
+      { 'm'    => [ /(?:\A|[^ap])m{1}/, '(\d{1,2})', :month ] },
+      { 'yyyy' => [ /y{4,}/, '(\d{4})',   :year ] },
+      { 'yy'   => [ /y{2,}/, '(\d{2})',   :year ] },
+      { 'hh'   => [ /h{2,}/, '(\d{2})',   :hour ] },
+      { 'h'    => [ /h{1}/,  '(\d{1,2})', :hour ] },
+      { 'nn'   => [ /n{2,}/, '(\d{2})',   :min ]  },
+      { 'n'    => [ /n{1}/,  '(\d{1,2})', :min ] },
+      { 'ss'   => [ /s{2,}/, '(\d{2})',   :sec ] },
+      { 's'    => [ /s{1}/,  '(\d{1,2})', :sec ] },
+      { 'u'    => [ /u{1,}/, '(\d{1,3})', :usec ] },
+      { 'dd'   => [ /d{2,}/, '(\d{2})',   :day ] },
+      { 'd'    => [ /(?:[^\\]|\A)d{1}/, '(\d{1,2})', :day ] },
+      { 'ampm' => [ /ampm/,  '((?:a|p)\.?m\.?)', :meridian ] },
+      { 'zo'   => [ /zo/,    '(?:[-+]\d{2}:\d{2})'] },
+      { 'tz'   => [ /tz/,    '(?:\[A-Z]{1,4})' ] }, 
+      { '_'    => [ /_/,     '\s?' ] }
+    ]
+    
+    # Arguments whichs will be passed to the format proc if matched in the 
+    # time string. The key must match the key from the format tokens. The array 
+    # consists of the arry position of the arg, the arg name, and the code to 
+    # place in the time array slot. The position can be nil which means the arh
+    # won't be placed in the array.
+    #
+    # The code can be used to run manipulations 
+    # of the arg value if required, otherwise should just be the arg name.
+    #
+    @@format_proc_args = {
+      :year     => [0, 'y', 'unambiguous_year(y)'],
+      :month    => [1, 'm', 'm'],
+      :day      => [2, 'd', 'd'],
+      :hour     => [3, 'h', 'full_hour(h,md)'],
+      :min      => [4, 'n', 'n'],
+      :sec      => [5, 's', 's'],
+      :usec     => [6, 'u', 'u'],
+      :meridian => [nil, 'md', nil]
+    }
+    
+    # Compile formats into validation regexps and format procs    
+    def self.format_expression_generator(string_format)
+      regexp = string_format.dup      
       order  = {}
       ord = lambda {|k| order[k] = $~.begin(0) }
-      regexp.gsub!(/([\.\/])/,         '\\1')      
-      regexp.gsub!(/m{3,}/,            '(\w{3,9})') && ord.call(:month)
-      regexp.gsub!(/m{2}/,             '(\d{2})')   && ord.call(:month)
-      regexp.gsub!(/(?:\A|[^ap])m{1}/, '(\d{1,2})') && ord.call(:month)
-      regexp.gsub!(/y{4,}/,            '(\d{4})')   && ord.call(:year)
-      regexp.gsub!(/y{2,}/,            '(\d{2})')   && ord.call(:year)
-      regexp.gsub!(/h{2,}/,            '(\d{2})')   && ord.call(:hour)
-      regexp.gsub!(/h{1}/,             '(\d{1,2})') && ord.call(:hour)
-      regexp.gsub!(/n{2,}/,            '(\d{2})')   && ord.call(:min)
-      regexp.gsub!(/n{1}/,             '(\d{1,2})') && ord.call(:min)
-      regexp.gsub!(/s{2,}/,            '(\d{2})')   && ord.call(:sec)
-      regexp.gsub!(/s{1}/,             '(\d{1,2})') && ord.call(:sec)
-      regexp.gsub!(/u{1,}/,            '(\d{1,3})') && ord.call(:usec)
-      regexp.gsub!(/d{2,}/,            '(\d{2})')   && ord.call(:day)            
-      regexp.gsub!(/(?:[^\\]|\A)d{1}/, '(\d{1,2})') && ord.call(:day)
-      regexp.gsub!(/ampm/,             '((?:a|p)\.?m\.?)') && ord.call(:meridian)
-      regexp.gsub!(/_/,                '\s?')
+      regexp.gsub!(/([\.\/])/, '\\1')      
+      
+      format_tokens.each do |token|
+        token_regexp, regexp_str, arg_key = *token.values.first
+        regexp.gsub!(token_regexp, regexp_str) && !arg_key.nil?  && ord.call(arg_key)
+      end
+      
       format_regexp = Regexp.new(regexp)
       format_proc = format_proc(order)
       return format_regexp, format_proc
@@ -101,7 +148,9 @@ module ValidatesTimeliness
     end
     
     # Generates a proc which when executed maps the regexp capture groups to a 
-    # time array based on the order of the capture groups. 
+    # proc argument based on order captured. A time array is built using the proc
+    # argument in the position indicated by the first element of the proc arg
+    # array.
     #
     # Examples:
     #
@@ -109,16 +158,7 @@ module ValidatesTimeliness
     #   'dd/mm/yyyy h:nn_ampm' => lambda {|d,m,y,h,n,md| md||=0; [unambiguous_year(y),m,d,full_hour(h,md),n,nil,nil] }
     #
     def self.format_proc(order)
-      arg_map = {
-        :year  => [0, 'y', 'unambiguous_year(y)'],
-        :month => [1, 'm', 'm'],
-        :day   => [2, 'd', 'd'],
-        :hour  => [3, 'h', 'full_hour(h,md)'],
-        :min   => [4, 'n', 'n'],
-        :sec   => [5, 's', 's'],
-        :usec  => [6, 'u', 'u'],
-        :meridian => [nil, 'md', nil]
-      }
+      arg_map = format_proc_args
       args = order.invert.sort.map {|p| arg_map[p[1]][1] }
       arr = [nil] * 7
       order.keys.each {|k| i = arg_map[k][0]; arr[i] = arg_map[k][2] unless i.nil? }
@@ -128,13 +168,13 @@ module ValidatesTimeliness
     
     def self.compile_formats(formats)
       formats.collect do |format|
-        regexp, format_proc = format_regexp_generator(format)
+        regexp, format_proc = format_expression_generator(format)
       end
     end
     
     def self.compile_format_expressions
-      @@valid_time_expressions = compile_formats(@@valid_time_formats)
-      @@valid_date_expressions = compile_formats(@@valid_date_formats)
+      @@valid_time_expressions     = compile_formats(@@valid_time_formats)
+      @@valid_date_expressions     = compile_formats(@@valid_date_formats)
       @@valid_datetime_expressions = compile_formats(@@valid_datetime_formats)
     end