Datetime arithmetic with a string in Ruby

In Ruby, I'm trying to do the following.

def self.stats(since)
  return Events.find(:all, :select => 'count(*) as this_count', :conditions => ['Date(event_date) >= ?', (Time.now - since)]).first.this_count
end

where "since" is a string representing an amount of time ('1 hour', '1 day', '3 days') and so on. Any suggestions?

From stackoverflow aronchick

• Try using Chronic to parse the date strings into actual datetime objects.

  From John Millikin

• I hacked this together with the ActiveSupport gem:

  require 'active_support'
  
  def string_to_date(date_string)
    parts = date_string.split
    return parts[0].to_i.send(parts[1])
  end
  sinces = ['1 hour', '1 day', '3 days']
  
  sinces.each do |since|
    puts "#{since} ago: #{string_to_date(since).ago(Time.now)}"
  end
  

  [edit] To answer your question, you might try it like that:

  :conditions => ['Date)event_date) >= ?', (string_to_date(since).ago(Time.now))]
  

  From wieczo

• I especially like the string_to_date(var).ago(Time.now) pattern.. thanks!

  glenn jackman : You might have added a comment to wieczo's answer rather than adding a new answer

  aronchick : I think i did this before comments had been implemented. Guessing though.
  From aronchick