module PrettyDate

def to_pretty
  a = (Time.now - self).to_i
  case a
  when 0 then 'just now'
  when 1 then 'a second ago'
  when 2..59 then a.to_s + ' seconds ago'
  when 60..119 then 'a minute ago' # 120 = 2 minutes
  when 120..3540 then (a / 60).to_i.to_s + ' minutes ago'
  when 3541..7100 then 'an hour ago' # 3600 = 1 hour
  when 7101..82_800 then ((a + 99) / 3600).to_i.to_s + ' hours ago'
  when 82_801..172_000 then 'a day ago' # 86400 = 1 day
  when 172_001..518_400 then ((a + 800) / (60 * 60 * 24)).to_i.to_s + ' days ago'
  when 518_400..1_036_800 then 'a week ago'
  when 1_036_801..4_147_204 then ((a + 180_000) / (60 * 60 * 24 * 7)).to_i.to_s + ' weeks ago'
  else strftime("%d %b %Y")
  end
end