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

I came up with this:

(0..84600).step(1800){|n| puts "#{n.to_s} #{Time.at(n).strftime("%I:%M%p")}"}

which gives me the wrong time, because Time.at(n) expects n to be number of seconds from epoch:

0     -> 07:00PM
1800  -> 07:30PM
3600  -> 08:00PM
...
82800 -> 06:00PM
84600 -> 06:30PM

What would be the most optimal, time zone independent solution for this transformation?

Answer 1

The simplest one-liner simply ignores the date:

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

#-> "11:00PM"

Answer 2

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 3

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