How do I add x months to a date


#1

I have a date

my_date = Date.new( 2007, 1, 1 )

I then have a variable holding an integer

months_to_add = 4

How do i add ‘months_to_add’ to my_date’?

I have spent ages googeling and looking in o’reilly ruby cookbook but no
luck;(

Any ideas?

Ben


#2

You can’t do it directly, date objects are immutable.

You could always get the date value from the object and then parse it,
add
the number of months you want and then create a new date object. That
seems
like a bit of a waste though. I would keep the date value in a string
and
manipulate it there, if and when I needed an actual date object with
that
value I would create a date object and give that out.

On 7/3/07, Ben E. removed_email_address@domain.invalid wrote:

(email address this email is sent from may be defunct)


“Hey brother christian with your high and mighty errand, Your actions
speak
so loud, I can’t hear a word you’re saying.”

-Greg Graffin (Bad Religion)


#3

And when I say string you could do better and use a hash or an array.

On 7/3/07, Glen H. removed_email_address@domain.invalid wrote:

On 7/3/07, Ben E. removed_email_address@domain.invalid wrote:

(email address this email is sent from may be defunct)


“Hey brother christian with your high and mighty errand, Your actions
speak
so loud, I can’t hear a word you’re saying.”

-Greg Graffin (Bad Religion)


#4

Ben E. wrote:

I have a date

my_date = Date.new( 2007, 1, 1 )

I then have a variable holding an integer

months_to_add = 4

How do i add ‘months_to_add’ to my_date’?

I have spent ages googeling and looking in o’reilly ruby cookbook but no
luck;(

Any ideas?

Ben

I would do it like this, if I didn’t mind loading some helpful
ActiveSupport junk:

irb> require ‘active_support/core_ext/numeric’
=> true
irb> require ‘active_support/core_ext/date’
=> true

irb> my_date = Date.new( 2007, 1, 1 )
=> #<Date: 4908203/2,0,2299161>

irb> my_time = my_date.to_time
=> Mon Jan 01 00:00:00 +0000 2007

irb> months_to_add = 4
=> 4

irb> new_time = my_time + months_to_add.months
=> Tue May 01 01:00:00 +0100 2007

irb> new_date = Date.new(new_time.year, new_time.month, new_time.day)
=> #<Date: 4908443/2,0,2299161>

best,
Dan


#5

On 03/07/07, Glen H. removed_email_address@domain.invalid wrote:

manipulate it there, if and when I needed an actual date object with that
value I would create a date object and give that out.

This all seems like a lot of messing around for what should be a
standard operation. This type of thing must exist in one of the
standard libraries.

Ben


#6

Ben E. wrote:

On 03/07/07, Glen H. removed_email_address@domain.invalid wrote:

manipulate it there, if and when I needed an actual date object with that
value I would create a date object and give that out.

This all seems like a lot of messing around for what should be a
standard operation. This type of thing must exist in one of the
standard libraries.

Ben

Actually, you are totally right. The ‘>>’ operator does what is
required:

irb> my_date = Date.new( 2007, 1, 1 )
=> #<Date: 4908203/2,0,2299161>

irb> my_date.to_s
=> “2007-01-01”
irb> (my_date >> 4).to_s
=> “2007-05-01”

best,
Dan


#7

Daniel L. wrote:

Ben E. wrote:

On 03/07/07, Glen H. removed_email_address@domain.invalid wrote:

manipulate it there, if and when I needed an actual date object with that
value I would create a date object and give that out.

This all seems like a lot of messing around for what should be a
standard operation. This type of thing must exist in one of the
standard libraries.

Ben

Actually, you are totally right. The ‘>>’ operator does what is
required:

irb> my_date = Date.new( 2007, 1, 1 )
=> #<Date: 4908203/2,0,2299161>

irb> my_date.to_s
=> “2007-01-01”
irb> (my_date >> 4).to_s
=> “2007-05-01”

best,
Dan

I couldn’t find any info about this operator >> with dates.

So, for example, if I have 2007-01-01 and I want to know the last day of
adding three months (2007-03-31) I would do:

d = Date.new(2007,1,1)
((d >> 3)-1).to_s

it works, but we can relay on this operations ?

regards,

rai


#8

Ben E. wrote:

I have a date

my_date = Date.new( 2007, 1, 1 )

I then have a variable holding an integer

months_to_add = 4

How do i add ‘months_to_add’ to my_date’?

I have spent ages googeling and looking in o’reilly ruby cookbook but no
luck;(

Any ideas?

Ben

I have not tried this but I know of something in rails that sounds
similar:
http://railshelp.com/ActiveSupport::CoreExtensions::Date::Calculations#months_ago

What if you could do something like this:

my_date = Date.new( 2007, 1, 1 )
months_to_add = 4
my_date = my_date.months_ago(months_to_add * -1)

Negative of months_ago could do it.

Shot in the dark but GL!


#9

Lloyd L. wrote:

Ben E. wrote:

I have a date

my_date = Date.new( 2007, 1, 1 )

I then have a variable holding an integer

months_to_add = 4

How do i add ‘months_to_add’ to my_date’?

I have spent ages googeling and looking in o’reilly ruby cookbook but no
luck;(

Any ideas?

Ben

I have not tried this but I know of something in rails that sounds
similar:
http://railshelp.com/ActiveSupport::CoreExtensions::Date::Calculations#months_ago

I wasn’t aware of this, thanks !!!

I’m using Rails so I’ll try to use it.

I prefer to do in Ruby if it’s possible …

What if you could do something like this:

my_date = Date.new( 2007, 1, 1 )
months_to_add = 4
my_date = my_date.months_ago(months_to_add * -1)

Negative of months_ago could do it.

Shot in the dark but GL!

I’ll try it …

thanks,

rai


#10

On 12/7/07, Raimon Fs removed_email_address@domain.invalid wrote:

I couldn’t find any info about this operator >> with dates.

So, for example, if I have 2007-01-01 and I want to know the last day of
adding three months (2007-03-31) I would do:

d = Date.new(2007,1,1)
((d >> 3)-1).to_s

it works, but we can relay on this operations ?

It’s standard Ruby

shadowfax:~/ssanta rick$ qri “Date#<<”
---------------------------------------------------------------- Date#<<
<<(n)

 Return a new Date object that is n months earlier than the current
 one.

 If the day-of-the-month of the current Date is greater than the
 last day of the target month, the day-of-the-month of the returned
 Date will be the last day of the target month.

shadowfax:~/ssanta rick$ qri “Date#>>”
---------------------------------------------------------------- Date#>>
>>(n)

 Return a new Date object that is n months later than the current
 one.

 If the day-of-the-month of the current Date is greater than the
 last day of the target month, the day-of-the-month of the returned
 Date will be the last day of the target month.


Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/