Asp Forum - Calculating a future date

Toine

2/6/2007 10:29:00 AM

Hello,

I'm new to Ruby so please bare with me...

I need to calculate a date that is exactly 31 days from the current
date in YYYY-MM-DD format. I know that Date.today returns the
current date, but how can I add 31 days to this value? I'm sure this
task is simple, but I haven't been able to figure it out.

Thanks

6 Answers

Farrel Lifson

2/6/2007 10:40:00 AM

On 06/02/07, Toine <bapolis@gmail.com> wrote:
> Hello,
>
> I'm new to Ruby so please bare with me...
>
> I need to calculate a date that is exactly 31 days from the current
> date in YYYY-MM-DD format. I know that Date.today returns the
> current date, but how can I add 31 days to this value? I'm sure this
> task is simple, but I haven't been able to figure it out.
>
> Thanks
>
>
>

Time now + number of seconds in 31 days
Time.now + 31*24*60*60
which is equivalent to
Time.now + 2678400

Farrel

David and Sharon Phillips

2/6/2007 10:47:00 AM

Hi,

This is something that took me ages to figure out because it is so
simple :)
Just add the number of days, eg future_date= Date.today+31

Cheers,
Dave

On 06/02/2007, at 9:40 PM, Farrel Lifson wrote:

> On 06/02/07, Toine <bapolis@gmail.com> wrote:
>> Hello,
>>
>> I'm new to Ruby so please bare with me...
>>
>> I need to calculate a date that is exactly 31 days from the current
>> date in YYYY-MM-DD format. I know that Date.today returns the
>> current date, but how can I add 31 days to this value? I'm sure this
>> task is simple, but I haven't been able to figure it out.
>>
>> Thanks
>>
>>
>>
>
> Time now + number of seconds in 31 days
> Time.now + 31*24*60*60
> which is equivalent to
> Time.now + 2678400
>
> Farrel
>

Toine

2/6/2007 10:55:00 AM

On Feb 6, 2:47 am, Sharon Phillips <phillip...@yahoo.co.uk> wrote:
> Hi,
>
> This is something that took me ages to figure out because it is so
> simple :)
> Just add the number of days, eg future_date= Date.today+31
>
> Cheers,
> Dave
>
> On 06/02/2007, at 9:40 PM, Farrel Lifson wrote:
>
> > On 06/02/07, Toine <bapo...@gmail.com> wrote:
> >> Hello,
>
> >> I'm new to Ruby so please bare with me...
>
> >> I need to calculate a date that is exactly 31 days from the current
> >> date in YYYY-MM-DD format. I know that Date.today returns the
> >> current date, but how can I add 31 days to this value? I'm sure this
> >> task is simple, but I haven't been able to figure it out.
>
> >> Thanks
>
> > Time now + number of seconds in 31 days
> > Time.now + 31*24*60*60
> > which is equivalent to
> > Time.now + 2678400
>
> > Farrel

Date.today + 31 and Time.now + 31*24*60*60 yield the same results.

Thanks for your help.

Toine

2/6/2007 10:56:00 AM

Alexandru E. Ungur

2/6/2007 1:25:00 PM

>>> sender: "Toine" date: "Tue, Feb 06, 2007 at 08:00:06PM +0900" <<<EOQ
> Date.today + 31 and Time.now + 31*24*60*60 yield the same results.
Just beware that although they yield the same result they do it at
*very* different speeds:

~>> cat date_vs_time.rb
require 'benchmark'
require 'date'

n = 100_000
Benchmark.bm do |x|
x.report { n.times do a = Date.today+31; end }
x.report { n.times do a = Time.now+2678400; end }
end

~>> ruby date_vs_time.rb
user system total real
24.300000 0.760000 25.060000 ( 31.808122)
0.410000 0.440000 0.850000 ( 0.971718)

So, whenever you can get away with Time, use it. Only use Date when
you have to.

Cheers,
Alex

Rob Biedenharn

2/8/2007 10:24:00 PM

On Feb 8, 2007, at 4:17 PM, Johan Veenstra wrote:

> On 2/6/07, Alexandru E. Ungur <alexandru@globalterrasoft.ro> wrote:
>>
>> >>> sender: "Toine" date: "Tue, Feb 06, 2007 at 08:00:06PM +0900"
>> <<<EOQ
>> > Date.today + 31 and Time.now + 31*24*60*60 yield the same results.
>> Just beware that although they yield the same result they do it at
>> *very* different speeds:
>>
>> ~>> cat date_vs_time.rb
>> require 'benchmark'
>> require 'date'
>>
>> n = 100_000
>> Benchmark.bm do |x|
>> x.report { n.times do a = Date.today+31; end }
>> x.report { n.times do a = Time.now+2678400; end }
>> end
>>
>>
>> ~>> ruby date_vs_time.rb
>> user system total real
>> 24.300000 0.760000 25.060000 ( 31.808122)
>> 0.410000 0.440000 0.850000 ( 0.971718)
>>
>>
>> So, whenever you can get away with Time, use it. Only use Date when
>> you have to.
>>
>>
>> Cheers,
>> Alex
>>
>>
>
> require 'date'
>
> puts Date.today
> puts Date.today + 100
> puts Time.now
> puts Time.now + 100*24*60*60
>
> 2007-02-08
> 2007-05-19
> Thu Feb 08 22:05:49 W. Europe Standard Time 2007
> Sat May 19 23:05:49 W. Europe Daylight Time 2007
>
> Looks innocent enough, but when I run the same program again in 60
> minutes,
> Time.now + 100*60*60 would output:
> Sun May 20 00:05:49 W. Europe Daylight Time 2007 (which is my
> birthday by
> the way).
>
> So from a correctness point of view, use Date when you are dealing
> with
> dates,
> and use Time when you are dealing with time.

Assuming you want to (or need to) use Time, then you can... if you
use ActiveSupport

#!/usr/bin/env ruby -w
require 'rubygems'
gem 'activesupport', '>=1.4'

require 'date'
puts "with Date:"
puts "today: #{Date.today}"
puts "+ 100: #{Date.today + 100}"
puts "with Time:"
puts " now: #{Time.now}"
puts "+ 8_640_000: #{Time.now + 100*24*60*60}"

puts "Time with some ActiveSupport from those Rails guys:"
require 'active_support'
puts " now: #{Time.now}"
puts " + 100.days: #{Time.now + 100.days}"
puts "in 100.days: #{Time.now.in(100.days)}"
__END__

with Date:
today: 2007-02-08
+ 100: 2007-05-19
with Time:
now: Thu Feb 08 17:11:43 -0500 2007
+ 8_640_000: Sat May 19 18:11:43 -0400 2007
Time with some ActiveSupport from those Rails guys:
now: Thu Feb 08 17:11:43 -0500 2007
+ 100.days: Sat May 19 18:11:43 -0400 2007
in 100.days: Sat May 19 17:11:43 -0400 2007

Notice that the last line has recognized (and corrected for) the
Daylight Savings transition

-Rob

Rob Biedenharn http://agileconsult...
Rob@AgileConsultingLLC.com

comp.lang.ruby

Calculating a future date

Toine

Farrel Lifson

David and Sharon Phillips

Toine

Toine

Alexandru E. Ungur

Rob Biedenharn

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