gistfile1.rb

require 'time'  
require 'date'
STAMP = "2009/06/29 23:19:35 +0000"

class Time

   def self.parse_utc(string)
     string =~ /(\d{4})\/(\d{2})\/(\d{2}) (\d{2}):(\d{2}):(\d{2})/
     utc($1, RFC2822_MONTH_NAME[$2.to_i - 1], $3, $4, $5, $6) 
   end
                       
   # Returns a UTC time object
   def self.parse_gm(string)
     string =~ /(\d{4})\/(\d{2})\/(\d{2}) (\d{2}):(\d{2}):(\d{2}) ([\+\-]\d{4})/
     # $1 = year
     # $2 = month
     # $3 = day
     # $4 = hours
     # $5 = minutes
     # $6 = seconds
     # $7 = time zone
     gm($1, RFC2822_MONTH_NAME[$2.to_i - 1], $3, $4, $5, $6, $7) 
   end 

   # Returns a local time object
   def self.parse_mktime(string)
     string =~ /(\d{4})\/(\d{2})\/(\d{2}) (\d{2}):(\d{2}):(\d{2}) ([\+\-]\d{4})/
     mktime($1, RFC2822_MONTH_NAME[$2.to_i - 1], $3, $4, $5, $6, $7) 
   end
   
   def self.parse_maketime(string)
     string =~ /(\d{4})\/(\d{2})\/(\d{2}) (\d{2}):(\d{2}):(\d{2}) ([\+\-]\d{4})/
     make_time($1, RFC2822_MONTH_NAME[$2.to_i - 1], $3, $4, $5, $6, nil, $7, now) 
   end
   
   # returns a local time value much faster than Time.parse
   def self.mktime_with_offset(string)
     string =~ /(\d{4})\/(\d{2})\/(\d{2}) (\d{2}):(\d{2}):(\d{2}) ([\+\-])(\d{2})/
     # $1 = year
     # $2 = month
     # $3 = day
     # $4 = hours
     # $5 = minutes
     # $6 = seconds
     # $7 = time zone direction
     # $8 = tz difference
     time = mktime($1, RFC2822_MONTH_NAME[$2.to_i - 1], $3, $4, $5, $6, $7)
     tz_difference = ("#{$7 == '-' ? '+' : '-'}#{$8}".to_i * 3600)
     time + tz_difference + zone_offset(time.zone) 
   end   
end   

require 'benchmark' 
n = 500
Benchmark.bm(10) do |test|
  test.report("Time.parse: ") do n.times {Time.parse(STAMP)} end
  test.report("Time.parse_gm: ") do n.times {Time.parse_gm(STAMP)} end  
  test.report("Time.parse_mktime: ") do n.times {Time.parse_mktime(STAMP)} end
  test.report("Time.parse_maketime: ") do n.times {Time.parse_maketime(STAMP)} end
  test.report("Time.parse_utc: ") do n.times {Time.parse_utc(STAMP)} end  
  test.report("Time::mktime_with_offset: ") do n.times {Time.mktime_with_offset(STAMP)} end
end   

results.txt

                user     system      total        real
Time.parse:   0.380000   0.960000   1.340000 (  3.684890)
Time.parse_gm:   0.290000   0.950000   1.240000 (  3.539086)
Time.parse_mktime:   0.020000   0.010000   0.030000 (  0.025100)
Time.parse_maketime:   0.290000   0.950000   1.240000 (  3.572833)
Time.parse_utc:   0.280000   0.960000   1.240000 (  3.552548)
Time.mktime_with_offset:   0.020000   0.000000   0.020000 (  0.024883)