How do I set date time to 1 month ago with DateTime.now.strftime("%Y-%m-%d")?

Question

I am trying to use set Google Analytics start date and end date to capture unique visitors within the last 30 days. I have made end_date = DateTime.now.strftime("%Y-%m-%d"), how do I set start_date to 30 days ago.

Solution 1

The problem is you're going too far with your creation of end_date.

You're turning it into a string, which has no math capabilities. Instead, leave it as a DateTime and you inherit the ability to add and subtract integers to do date math:

require 'date'

datetime_now = DateTime.now
end_date = datetime_now.strftime("%Y-%m-%d") # => "2013-08-06"
end_date.class # => String

end_date = datetime_now # => #<DateTime: 2013-08-06T14:55:20-07:00 ((2456511j,78920s,731393000n),-25200s,2299161j)>
end_date - 30 # => #<DateTime: 2013-07-07T14:55:20-07:00 ((2456481j,78920s,731393000n),-25200s,2299161j)>

Notice that end_date - 30 returns a DateTime that is exactly 30 days earlier; The time component is preserved. Convert the value to a string once you have the value you want.

Solution 2

I realise this question is very old, but here's a clean way to do it for anyone who needs to know:

start_date = (Date.now - 30.days).strftime("%Y-%m-%d")

or

start_date = (Date.now - 1.month).strftime("%Y-%m-%d")

You can do similar things with DateTime.now, and Time.now

Solution 3

With basic Ruby you can do this:

> irb
require 'date' # needed
today_minus_30  = Date.today.to_date - 30

# if you need the date as a string
date_as_string = today_minutes_30.strftime("%Y-%m-%d")

Comments

[PJP]

We need to see sample code showing what you've tried. See sscce.org

[Topka]

Problem is not al moths are 30 days. Any solution for this, I wonder?

[PJP]

You might want to explain where days and ago come from and how they can be included. The OP is using straight Ruby so those aren't available.

[Powers]

@theTinMan - I agree with your comment and updated my answer accordingly. Thanks.

[PJP]

No, no, no, don't recommend loading the entire Active Support code base, just to cherry-pick a few needed methods. Use the core extensions for Date, DateTime and Time. Matter of fact, read "How to Load Core Extensions".

[Powers]

@theTinMan - updated again and thanks for the comment. I couldn't get require 'active_support/core_ext/date.rb' to work, but found the require 'active_support/time' workaround on this thread: stackoverflow.com/questions/4238867/… Thanks!

[Geoff Williams]

I think this needs active_support/time or rails?