Normalize a flow of timestamps into ones suitable for charting

norm_time.rb

# HH:17:30 ... HH:27:30 => HH:20:00
def norm_time t
  i = t.to_i
  i /= 300.0
  i = i.round # round to nearest 5 minutes
  i /= 2      # floor to nearest 10 minutes
  Time.at i*600
end

s = Time.now
1000.times do
  puts "#{s} => #{norm_time s}"
  s += 15
end