set_time.rb

#!/usr/bin/env ruby

require 'time'

# Set system time. If the new time is in the past, "Freeze" system time for some time.
# Useful when your system time is ahead of actural time and you cannot adjust time to the past directly.
#
# Example:
#
#   $0 '2013-10-1 9:30:00'

# set date needs root
raise "root required" if Process.uid != 0
raise "Please provide some time such as '2013-10-1 9:30:00'" if ARGV.empty?

expected = Time.parse(ARGV.join(' '))
actural = Time.now

def set_date(date)
  system "date #{date.strftime('%m%d%H%M%Y.%S')} >/dev/null"
end

seconds = actural - expected
if seconds <= 0
  puts "Fast forward to #{expected}"
  set_date expected
else
  print "Freeze system time for #{seconds} seconds."
  (seconds * 2).to_i.times do |i|
    Thread.new { set_date actural }
    sleep 0.5
    print '.' if i % 4 == 0
  end
  puts ' Done.'
end