How do i print the date and time of specific lines that contain a certain key word using Ruby?

In other words i need Ruby to read from the attached log file and report the dates and time that has the keyword MAY_DAY. I am able to print out all the information but I don't have the slightest idea on how to print out the specific entries.

I am an uber noob and find ruby extremely difficult to understand. I appreciate all help and respectful criticism. Thanks

test.txt

Oct 15 12:54:01 WHERE IS THE LOVIN MAY_DAY
Oct 16 23:15:44 WHAT THE HECK CAN I DO ABOUT IT HUMP_DAY
Oct 16 14:16:09 I LOVE MY BABY GIRL MAY_DAY
Oct 16 08:25:18 CAN WAIT UNTIL MY BABY RECOVERS CRYSTAL_WIFE
Oct 18 17:48:38 I HOPE HE STOP MESSING WITH THESE FOOLISH CHILDREN TONY_SMITH
Oct 19 05:17:58 GAME TIME GO HEAD AND GET ME MAY_DAY
Oct 20 10:23:33 GAMESTOP IS WHERE ITS AT GAME_DAY
Oct 21 03:54:27 WHAT IS GOING ON WITH MY LUNCH HUNGRY_MAN
RestartMonitor.rb

class RestartMonitor    

   counter = 1
   begin
      file = File.new("test.txt", "r")
      while (line = file.gets)
         puts "#{counter}: #{line}"
         counter = counter + 1
      end

 end


When i run the file i get the following results:

Oct 15 12:54:01 WHERE IS THE LOVIN MAY_DAY
Oct 16 23:15:44 WHAT THE HECK CAN I DO ABOUT IT HUMP_DAY
Oct 16 14:16:09 I LOVE MY BABY GIRL MAY_DAY
Oct 16 08:25:18 CAN WAIT UNTIL MY BABY RECOVERS CRYSTAL_WIFE
Oct 18 17:48:38 I HOPE HE STOP MESSING WITH THESE FOOLISH CHILDREN TONY_SMITH
Oct 19 05:17:58 GAME TIME GO HEAD AND GET ME MAY_DAY
Oct 20 10:23:33 GAMESTOP IS WHERE ITS AT GAME_DAY
Oct 21 03:54:27 WHAT IS GOING ON WITH MY LUNCH HUNGRY_MAN

When i run the code i would like it to only display the date and times that have the keyworld MAY_DAY. so the output should be:

Oct 15 12:54:01
Oct 16 14:16:09
Oct 19 05:17:58