newbie: How do I convert "about 2 hours ago" to "today"?

I'm not sure if there is an existing way that is clean.... but here is the beginings of a possible solution?

SECONDS_IN_DAY = 60*60*24
time_of_post = Time.gm(2000,"jan",1,20,15,1).to_i

if (Time.now.to_i - time_of_post) <= SECONDS_IN_DAY
  # print 'today'
elsif (Time.now.to_i - time_of_post) <= SECONDS_IN_DAY*2
  # print 'yesterday'
else
  # use distance_of_time_in_words
end