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

Question

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.

Answer 1

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

Answer 2

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

Answer 3

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.

Answer 4

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