CODEWITHSUNDEEP
rubyroundingunix-timestampepochdatetimeoffset
Kurt W
Kurt W

Reputation: 351

Ruby - How to round Unix Timestamp (Epoch) to nearest month

I am attempting to round UNIX timestamps in Ruby to the nearest whole month. I have the following UNIX timestamps which I'd like to convert as shown--basically if the day of the month is the 15th and onward, it should round up to the next month (e.g. February 23rd rounds up to March 1st; February 9th rounds down to February 1st).

Here are the timestamps I have and the result I need help achieving:

1455846925 (Feburary 19th, 2016) => 1456790400 (March 1st, 2016)

1447476352 (November 14th, 2015) => 1446336000 (November 1st, 2015)

1242487963 (May 16th, 2009) => 1243814400 (June 1st, 2009).

I am okay solely relying on the logic of 1-14 (round down) / 15+ (round up). I realize this won't always take into account the days in a month and I can accept that for this if needed (although a solution that always takes into account the days in a given month is a bonus).

Ruby's DateTime module may be able to do it in combination with modulo of the number of seconds in a month but I'm not quite sure how to put it all together. If I can convert the UNIX timestamp directly without first translating it to a Ruby Date, that is perfectly fine too.

Thank you in advance for your assistance.

Upvotes: 1

Views: 1400

Answers (4)

Andrew Hendrie
Andrew Hendrie

Reputation: 6415

Something like this will work if you use ActiveSupport in Rails:

require 'date'    

def round_to_nearest_month(timestamp)

  # Convert the unix timestamp into a Ruby DateTime object
  datetime = timestamp.to_datetime

  # Get the day of the month from the datetime object
  day_of_month = datetime.mday

  if day_of_month < 15
    datetime.at_beginning_of_month
  else 
    datetime.at_beginning_of_month.next_month
  end    

  return datetime

end

Upvotes: 0

Jordan Running
Jordan Running

Reputation: 106077

I don't know if this is as accurate as @CarySwoveland's solution, but I like it:

require 'time'

FIFTEEN_DAYS = 15 * 24 * 60 * 60

def round_to_month(secs)
  t1 = Time.at(secs + FIFTEEN_DAYS)
  Time.new(t1.year, t1.month)
end

p round_to_month(1455846925) # round 2016-02-18 17:55:25 -0800 
# => 2016-03-01 00:00:00 -0800

p round_to_month(1447476352) # round 2015-11-13 20:45:52 -0800
# => 2015-11-01 00:00:00 -0700

p round_to_month(1242487963) # round 2009-05-16 08:32:43 -0700 
# => 2009-05-01 00:00:00 -0700

If you want it to return a UNIX timestamp instead just tack .to_i onto the last line in the method.

Upvotes: 1

Cary Swoveland
Cary Swoveland

Reputation: 110705

This rounds to the nearest second.

require 'time'

def round_to_month(secs)
  t1 = Time.at secs
  t2 = (t1.to_datetime >> 1).to_time
  s1 = Time.new(t1.year, month=t1.month)
  s2 = Time.new(t2.year, month=t2.month)
  (t1-s1) < (s2-t1) ? s1 : s2
end

round_to_month(1455846925) # round 2016-02-18 17:55:25 -0800 
  #=> 2016-03-01 00:00:00 -0800
round_to_month(1447476352) # round 2015-11-13 20:45:52 -0800
  #=> 2015-11-01 00:00:00 -0700 
round_to_month(1242487963) # round 2009-05-16 08:32:43 -0700 
  #=> 2009-05-01 00:00:00 -0700

Consider

secs = 1455846925

The calculations are as follows:

 t1 = Time.at secs
   #=> 2016-02-18 17:55:25 -0800 
 dt = t1.to_datetime
   #=> #<DateTime: 2016-02-18T17:55:25-08:00 ((2457438j,6925s,0n),-28800s,2299161j)> 
 dt_next = dt >> 1
   #=> #<DateTime: 2016-03-18T17:55:25-08:00 ((2457467j,6925s,0n),-28800s,2299161j)> 
 t2 = dt_next.to_time 
   #=> 2016-03-18 18:55:25 -0700 
 s1 = Time.new(t1.year, month=t1.month)
   #=> Time.new(2016, month=2) 
   #=> 2016-02-01 00:00:00 -0800 
 s2 = Time.new(t2.year, month=t2.month)
   # Time.new(2016, month=3)
   #=> 2016-03-01 00:00:00 -0800 
 (t1-s1) < (s2-t1) ? s1 : s2
   #=> 1533325.0 < 972275.0 ? 2016-02-18 17:55:25 -0800 : 2016-03-01 00:00:00 -0800
   #=> 2016-03-01 00:00:00 -0800

Upvotes: 3

Babar Al-Amin
Babar Al-Amin

Reputation: 3984

It would be easy to convert it to Time object and then convert it back to timestamp

If you're using Rails, this method should do, what you want:

def nearest_month(t)
  time = Time.at(t).utc
  time = time.next_month if time.day >= 15

  time.beginning_of_month.to_i
end

Upvotes: 1

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