Issue #10733 has been updated by Maarten Claes.



After some experimentation it looks like this has something do with the fact that `DateTime#httpdate` returns an `US-ASCII` encoded string.

```
require 'time'

from_httpdate = DateTime.now.httpdate
as_string     = "Mon, 12 Jan 2015 12:09:19 GMT"

puts from_httpdate.encoding # => US-ASCII
puts Time.httpdate(from_httpdate) # Works
puts Time.httpdate(as_string) # Works

begin
  puts(Time.httpdate(from_httpdate)) # => ArgumentError
rescue => e
  p e
end

puts from_httpdate.encode!(Encoding.find('UTF-8'))

begin
  puts Time.httpdate(from_httpdate) # Works
rescue => e
  p e
end
```

----------------------------------------
Bug #10733: Time.httpdate raises ArgumentError when DateTime.now.httpdate is provided as input
https://bugs.ruby-lang.org/issues/10733#change-50965

* Author: Maarten Claes
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
An irb session demonstrating the bug:

```
irb(main):001:0> require 'time'
=> true
irb(main):002:0> Time.httpdate("Mon, 12 Jan 2015 12:04:15 GMT")
=> 2015-01-12 12:04:15 UTC
irb(main):003:0> DateTime.now.httpdate.to_s
=> "Mon, 12 Jan 2015 12:04:56 GMT"
irb(main):004:0> Time.httpdate(DateTime.now.httpdate.to_s)
ArgumentError: not RFC 2616 compliant date: "Mon, 12 Jan 2015 12:05:08 GMT"
        from /Users/mcls/.rbenv/versions/2.2.0/lib/ruby/2.2.0/time.rb:544:in `httpdate'
        from (irb):4
        from /Users/mcls/.rbenv/versions/2.2.0/bin/irb:11:in `<main>'
```

To reproduce:
```
require 'time'
Time.httpdate("Mon, 12 Jan 2015 12:04:15 GMT") # works
Time.httpdate(DateTime.now.httpdate.to_s) # => ArgumentError
```

It seems that this only occurs on 2.2.0. (Tested on 2.1.5 and it works fine)



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