From: Sam Roberts <sroberts@...>
Date: 2004-04-01T03:08:00+09:00
Subject: Re: How to get internal state of DateTime in seconds

Quoteing smejmoon@yahoo.com, on Thu, Apr 01, 2004 at 01:44:21AM +0900:
> How do you get internal state in seconds of DateTime instance? 
> Or convert it to Time instance? 

There is no method to do this, I proposed it in my email:

  'possible Time & DateTime RCR: reconciling and extending their apis'

please reply to it if you'd like to see such a method added in the future!

> I want to compare two times with variable precision.
> Below is my try to parse time from Common Log Format.
> 
> require 'date'
> str1 = '20/Nov/2003:08:08:09 +0200'
> str2 = '20/Nov/2003:08:04:09 +0200'
> t1 = DateTime.strptime(str=str1, fmt='%d/%b/%Y:%H:%M:%S %Z')
> t2 = DateTime.strptime(str=str2, fmt='%d/%b/%Y:%H:%M:%S %Z')
> 
> #what is difference in minutes between these 2 times?

It's not clear from the docs, but you can do this:

[ensemble] ~/p/ruby/vcard $ irb18 -r date
irb(main):001:0> t0 = DateTime.now
irb(main):002:0> t0.to_s
=> "2004-03-31T12:57:41-0500"
irb(main):003:0> t1 = DateTime.now
irb(main):004:0> t1.to_s
=> "2004-03-31T12:57:50-0500"
irb(main):005:0> r = t1-t0
=> Rational(192691, 1920000000)
irb(main):007:0> r.to_f * 24 * 60 * 60
=> 8.671095

The difference between two DateTime objects is a Rational, a fraction of days.
Multiply that by the number of seconds/day, and you get the number of seconds
difference.

You could implement Date#to_time() by taking the difference between self, and
Date.civil(1970,1,1), which should give you difference in days, then multiply
by seconds per day, then use Time.at().

Cheers,
Sam