Calculating a future date

ruby-talk
1

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

2

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

Farrel

···

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

3

Hi,

This is something that took me ages to figure out because it is so simple :slight_smile:
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

4

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

Thanks for your help.

···

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 :slight_smile:
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

5

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

Thanks for your help.

···

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 :slight_smile:
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

6

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

7

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.

···

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

8

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://agileconsultingllc.com
Rob@AgileConsultingLLC.com

···

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.