Ruby/Rails - How to convert seconds to time? - ruby-on-rails

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

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

Answer 3

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 4

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