```ruby
def minutes_in_words(timestamp)
minutes = (((Time.now - timestamp).abs)/60).round
return nil if minutes < 0
case minutes
when 0..4 then '< 5 minutes'
when 5..14 then '< 15 minutes'
when 15..29 then '< 30 minutes'
when 30..59 then '> 30 minutes'
when 60..119 then '> 1 hour'
when 120..239 then '> 2 hours'
when 240..479 then '> 4 hours'
when 480..719 then '> 8 hours'
when 720..1439 then '> 12 hours'
when 1440..11519 then '> ' << pluralize((minutes/1440).floor, 'day')
when 11520..43199 then '> ' << pluralize((minutes/11520).floor, 'week')
when 43200..525599 then '> ' << pluralize((minutes/43200).floor, 'month')
else '> ' << pluralize((minutes/525600).floor, 'year')
end
end
```
Or use Rails' time\_ago\_in\_words: