Add a month to a Date object

rubyonrails-talk
1

Howdy all,

This may be the dumbest question in the world, but how can you "add one month" to a Date object? I can't just add 30 days, because months have varying lengths.

Any help would be much appreciated...

Thanks!

-Neal

2

if you convert it to time you can use 'advance', and then convert it back to a date. For example:

date_object.to_time.advance(1.month).to_date

http://api.rubyonrails.com/classes/ActiveSupport/CoreExtensions/DateTime/Calculations.html#M000714

3

oops, wrong syntax. Should be:

date_object.to_time.advance(:months => 1).to_date

4

If you have a Date object (i.e, not a Time object), then use >> and << to go forward and backward by month. If you have a Time (since you're in Rails), you can use months_ago or months_since.

2.months_since(Time.now)

Compare that to (2.months).since(Time.now) particularly in the last few days of the month.

-Rob

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

5

Note:

IMO the best way to do this is trough << and >>. But watch out in iterating blocks, like while, for & etc. You might end up in the wrong day if you keep doing something like date >> 1

Example:

date = '2007-12-31'.to_date while date <= '2008-3-31'.to_date   puts date   date >> 1 end

This is going to be your output: (the formatting of the date is going to be different, this is just an example)

Dec 31, 2007 Jan 31, 2008 Feb 29, 2008 Mar 29, 2008 (note that your date has day = 29)

If instead you do something like:

date = '2007-12-31'.to_date c = 0 while date <= '2008-3-31'.to_date   puts date   c = c + 1 #this is the same as c += 1   date = date >> c #this is the same as date =>> c end (This code could be shorter, but would be harder to understand)

This is going to be your output:

Dec 31, 2007 Jan 31, 2008 Feb 29, 2008 Mar 31, 2008

The difference is that in the first approach, you always do date >> 1, several times. In the second, you do date >> 1 the first time, date >> 2 the second, and so on.

6

I had a brain fart. The second code is WRONG and wont work as expected. This should work.

date = '2007-12-31'.to_date c = 0 while date >> c <= '2008-3-31'.to_date   puts date >> c   c = c + 1 #this is the same as c += 1 end

This is going to be your output:

Dec 31, 2007 Jan 31, 2008 Feb 29, 2008 Mar 31, 2008