Comparing time or ditching date in ruby on rails

Question

I have some time defined from my database, and this is how it looks:

ruby-1.9.2-p290 :017 > djel.smjena.pocetak1.to_time 
 => 2000-01-01 08:00:00 +0100 

and that is ok, it assigned me 2000-1-1 also, I got something that happened in some datetime

ruby-1.9.2-p290 :019 > dog.pocetak 
 => Thu, 25 Aug 2011 08:18:00 UTC +00:00 

So I was hoping, that .to_time would ditch my date, but that does not happen

ruby-1.9.2-p290 :020 > dog.pocetak.to_time 
 => Thu, 25 Aug 2011 08:18:00 UTC +00:00 

so, now, comparing if something happened before 8:00 is useless. So, how can I compare that? is there a way to set dog.pocetak to 2000-01-01 without touch clock?

thank you

p.s. also, I thought of creating new time variable, only to get from old variable hours and minutes, but this methods dont work?

ruby-1.9.2-p290 :059 > dog.pocetak.hour
 => 8

but

ruby-1.9.2-p290 :060 > dog.pocetak.minute
NoMethodError: undefined method `minute' for 2011-08-25 08:18:00 UTC:Time
        from /home/dorijan/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.0.10/lib/active_support/time_with_zone.rb:322:in `method_missing'
        from (irb):60
        from /home/dorijan/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in `start'
        from /home/dorijan/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in `start'
        from /home/dorijan/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.10/lib/rails/commands.rb:23:in `<top (required)>'
        from script/rails:6:in `require'
        from script/rails:6:in `<main>'
ruby-1.9.2-p290 :061 > dog.pocetak.minutes
NoMethodError: undefined method `minutes' for 2011-08-25 08:18:00 UTC:Time
        from /home/dorijan/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.0.10/lib/active_support/time_with_zone.rb:322:in `method_missing'
        from (irb):61
        from /home/dorijan/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in `start'
        from /home/dorijan/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in `start'
        from /home/dorijan/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.10/lib/rails/commands.rb:23:in `<top (required)>'
        from script/rails:6:in `require'
        from script/rails:6:in `<main>'

really frustrating :)

Answer 1

With ActiveSupport and Time.change you can reset the year, month and day if you like:

> t = Time.now
=> Sun Aug 21 00:46:29 +0000 2011
> t.change(:month => 1, :day => 1, :year => 2000)
=> Sat Jan 01 00:46:29 +0000 2000

This way you could compare the "times" between each other, if they all were reset to the same date. Not sure if this is a good solution though, depends on what you really are looking for.

EDIT:

As per mu's suggestion you could also take a look at the time data type.

Answer 2

To get the minutes from a Time object, you want min not minutes. You can't have a Time instance that's just a "time of day" (i.e. no year, month, ...) but you can use strftime to get a string version that will compare properly:

tod = Time.now.strftime('%H:%M:%S')
# "17:07:23"

if(t1.strftime('%H:%M:%S') == t2.strftime('%H:%M:%S'))
    # Same time of day (to one second resolution)
end

Or you could compare the individual hour, min, and sec components:

if(t1.hour == t2.hour && t1.min == t2.min && t1.sec == t2.sec)
    # Same time of day (to one second resolution)
end

Which approach you take depends, as usual, on your specific situation and what else is going in in that vicinity.