Ruby/Rails - How to convert seconds to time?

Question

I need to perform the following conversion:

0     -> 12.00AM
1800  -> 12.30AM
3600  -> 01.00AM
...
82800 -> 11.00PM
84600 -> 11.30PM

Answer 1

Two offers:

The elaborate DIY solution:

def toClock(secs)
  h = secs / 3600;  # hours
  m = secs % 3600 / 60; # minutes
  if h < 12 # before noon
    ampm = "AM"
    if h = 0
      h = 12
    end
  else     # (after) noon
    ampm =  "PM"
    if h > 12
      h -= 12
    end
  end
  ampm = h <= 12 ? "AM" : "PM";
  return "#{h}:#{m}#{ampm}"
end

the Time solution:

def toClock(secs)
  t = Time.gm(2000,1,1) + secs   # date doesn't matter but has to be valid
  return "#{t.strftime("%I:%M%p")}   # copy of your desired format
end

HTH

Answer 2

In other solutions, the hour-counter would be reset to 00 when crossing 24-hour day boundaries. Also beware that Time.at rounds down, so it will give the wrong result if the input has any fractional seconds (f.ex. when t=479.9 then Time.at(t).utc.strftime("%H:%M:%S") will give 00:07:59 and not 00:08:00` which is the correct one).

If you want a way to convert any number of seconds (even high counts larger than 24-hour day spans) into an ever increasing HH:MM:SS counter, and handle potential fractional seconds, then try this:

# Will take as input a time in seconds (which is typically a result after subtracting two Time objects),
# and return the result in HH:MM:SS, even if it exceeds a 24 hour period.
def formatted_duration(total_seconds)
  total_seconds = total_seconds.round # to avoid fractional seconds potentially compounding and messing up seconds, minutes and hours
  hours = total_seconds / (60*60)
  minutes = (total_seconds / 60) % 60 # the modulo operator (%) gives the remainder when leftside is divided by rightside. Ex: 121 % 60 = 1
  seconds = total_seconds % 60
  [hours, minutes, seconds].map do |t|
    # Right justify and pad with 0 until length is 2. 
    # So if the duration of any of the time components is 0, then it will display as 00
    t.round.to_s.rjust(2,'0')
  end.join(':')
end

Modified from @springerigor's and suggestion in the discussion at https://gist.github.com/shunchu/3175001

Answer 3

The simplest one-liner simply ignores the date:

Time.at(82800).utc.strftime("%I:%M%p")

#-> "11:00PM"

Answer 4

Not sure if this is better than

(Time.local(1,1,1) + 82800).strftime("%I:%M%p")


def hour_minutes(seconds)
  Time.at(seconds).utc.strftime("%I:%M%p")
end


irb(main):022:0> [0, 1800, 3600, 82800, 84600].each { |s| puts "#{s} -> #{hour_minutes(s)}"}
0 -> 12:00AM
1800 -> 12:30AM
3600 -> 01:00AM
82800 -> 11:00PM
84600 -> 11:30PM

Stephan