Relative time builder in Ruby - requires ActiveSupport Time extensions

gistfile1.rb

require "active_support/time"

# in 3 days
Time.fluent("+3d")

# Tomorrow at 10 am
Time.fluent("+1d @10h")

class Time
  def self.fluent(at)
    at.split(' ').reduce(Time.now) do |time, part|
      if part =~ /^(?<command>[\+@])(?<arguments>.*)$/
        case $~[:command]
        when '+'
          time.advance( to_time_params($~[:arguments], true))
        when '@'
          time.change( to_time_params($~[:arguments]))
        end
      else
        time
      end
    end
  end

  private

  def self.to_time_params(arguments, plural=false)
    if arguments =~ /(?<duration>[0-9]*)(?<unit>[dhm])$/
      duration = $~[:duration].to_i
      unit = case $~[:unit]
        when 'd'
          plural ? :days : :day
        when 'h'
          plural ? :hours : :hour
        end
      { unit => duration }
    end
  end
end