Asp Forum - Time without Date

List Recv

10/26/2006 8:42:00 PM

Is there any class or lib to deal with Times without Date? (Eg "3:30
PM" - but I don't want it associated with a date.)

Ideally, I'd like to:
* Have clock arithmetic (1 AM minus 90 minutes is 11:30 PM)
* Convert from DateTime to dateless times (and, by adding a date, back)
* Store it with ActiveRecord

Any ideas?

9 Answers

Paul Lutus

10/26/2006 9:18:00 PM

List Recv wrote:

> Is there any class or lib to deal with Times without Date? (Eg "3:30
> PM" - but I don't want it associated with a date.)
>
> Ideally, I'd like to:
> * Have clock arithmetic (1 AM minus 90 minutes is 11:30 PM)
> * Convert from DateTime to dateless times (and, by adding a date, back)
> * Store it with ActiveRecord
>
> Any ideas?

Have you tried the Time class?

#!/usr/bin/ruby -w

is = Time.new

h = 4 # hours

was = is - (h * 60 * 60)

puts "Time now: #{is}\nTime then: #{was}"

Output:

Time now: Thu Oct 26 14:10:41 PDT 2006
Time then: Thu Oct 26 10:10:41 PDT 2006

The Time object is expressed in seconds elapsed since 1/1/1970 00:00 GMT.
Just add or subtract seconds to get what you want. And the 1970 limitation
isn't actually much of a limitation:

irb(main):008:0> t = Time.new - (100 * 60 * 60 * 24 * 365.25)
=> Fri Oct 26 13:16:52 PST 1906

--
Paul Lutus
http://www.ara...

List Recv

10/26/2006 9:33:00 PM

The problem with Time is that it tracks a date also.

Let me explain:

I have a scheduler, which, for example, can be set to do something at 3
PM. I'd like to store that time in an object, and then take a Time,
chop off the date part, and see if the time matches.

Make sense?

Paul Lutus wrote:
> List Recv wrote:
>
> > Is there any class or lib to deal with Times without Date? (Eg "3:30
> > PM" - but I don't want it associated with a date.)
> >
> > Ideally, I'd like to:
> > * Have clock arithmetic (1 AM minus 90 minutes is 11:30 PM)
> > * Convert from DateTime to dateless times (and, by adding a date, back)
> > * Store it with ActiveRecord
> >
> > Any ideas?
>
> Have you tried the Time class?
>
> #!/usr/bin/ruby -w
>
> is = Time.new
>
> h = 4 # hours
>
> was = is - (h * 60 * 60)
>
> puts "Time now: #{is}\nTime then: #{was}"
>
> Output:
>
> Time now: Thu Oct 26 14:10:41 PDT 2006
> Time then: Thu Oct 26 10:10:41 PDT 2006
>
> The Time object is expressed in seconds elapsed since 1/1/1970 00:00 GMT.
> Just add or subtract seconds to get what you want. And the 1970 limitation
> isn't actually much of a limitation:
>
> irb(main):008:0> t = Time.new - (100 * 60 * 60 * 24 * 365.25)
> => Fri Oct 26 13:16:52 PST 1906
>
> --
> Paul Lutus
> http://www.ara...

List Recv

10/26/2006 9:39:00 PM

Related question:

Is there a way to convert a Time (or DateTime) to Ruby's Date class?

Bil Kleb

10/26/2006 10:05:00 PM

List Recv wrote:
>
> Make sense?

To be sure, can you supply a test?

Regards,
--
Bil Kleb
http://kleb.tadalist.com/lists/pub...

List Recv

10/26/2006 10:09:00 PM

a = Time.parse('Wed Oct 25 13:10:00 2006')
b = Time.parse('Thu Oct 26 13:10:00 2006')
c = Time.parse('Fri Oct 27 13:05:00 2006')

at = TimeOnly.from_time(a)
bt = TimeOnly.from_time(b)
ct = TimeOnly.from_time(c)

assert_equal at, bt
assert ct < bt

Bil Kleb wrote:
> List Recv wrote:
> >
> > Make sense?
>
> To be sure, can you supply a test?
>
> Regards,
> --
> Bil Kleb
> http://kleb.tadalist.com/lists/pub...

Paul Lutus

10/27/2006 12:13:00 AM

List Recv wrote:

> The problem with Time is that it tracks a date also.
>
> Let me explain:
>
> I have a scheduler, which, for example, can be set to do something at 3
> PM. I'd like to store that time in an object, and then take a Time,
> chop off the date part, and see if the time matches.

Don't you mean chop off the time part:

#!/usr/bin/ruby -w

t = Time.new

h = (t.to_i % 86400)

s = h % 60
h /= 60
m = h % 60
h /= 60

puts "Time now: #{sprintf("%02d:%02d:%02d GMT",h,m,s)}"

If you extract the number of seconds from a Time object as shown above, you
have an integer, not a Time object, and its time is expressed in GMT.

--
Paul Lutus
http://www.ara...

Kevin

10/27/2006 2:53:00 AM

List Recv wrote:
> Related question:
>
> Is there a way to convert a Time (or DateTime) to Ruby's Date class?

I added a few conversion methods like this to 'ruby-units' gem

class Time
def to_datetime
DateTime.civil(1970,1,1)+(self.to_f+self.gmt_offset)/86400
end

def to_date
Date.civil(1970,1,1)+(self.to_f+self.gmt_offset)/86400
end
end

This seems to work pretty well, although I haven't tested it on a wide
range of OSs.

_Kevin

Ara.T.Howard

10/27/2006 3:50:00 AM

Jeremy Hinegardner

10/27/2006 6:23:00 AM

On Fri, Oct 27, 2006 at 12:50:03PM +0900, ara.t.howard@noaa.gov wrote:
> On Fri, 27 Oct 2006, _Kevin wrote:
>
> >
> >List Recv wrote:
> >>Related question:
> >>
> >>Is there a way to convert a Time (or DateTime) to Ruby's Date class?
> >
> >I added a few conversion methods like this to 'ruby-units' gem
> >
> >class Time
> >def to_datetime
> > DateTime.civil(1970,1,1)+(self.to_f+self.gmt_offset)/86400
> > end
> >
> > def to_date
> > Date.civil(1970,1,1)+(self.to_f+self.gmt_offset)/86400
> > end
> >end
> >
> >This seems to work pretty well, although I haven't tested it on a wide
> >range of OSs.
>
> it's nice to have
>
> Time.to_time
> Time.to_date
>
> Date.to_time
> Date.to_date
>
> DateTime.to_time
> DateTime.to_date
>
> so you can do
>
> do_not_care_which_one.to_time
> do_not_care_which_one.to_date
>
> a la rails.
>
> 2 cts.

And that's why we have facets!

% gem install facets
% cat date-time.rb
require 'date'
require 'rubygems'
require 'facets'
require 'date/to_time'
require 'date/to_date'
require 'time/to_date'
require 'time/to_time'

timers = {
:date => Date.today,
:time => Time.now,
:date_time => DateTime.now
}

["to_date", "to_time"].each do |method|
timers.each_pair do |name,time|
result = time.send(method)
class_name = result.class.name
puts "#{name.to_s.rjust(10)}.#{method} yields result #{result} with class of #{class_name}"
end
end

puts
puts "superclass of DateTime : #{DateTime.superclass}"

% ruby date-time.rb
date.to_date yields result 2006-10-27 with class of Date
time.to_date yields result 2006-10-27 with class of Date
date_time.to_date yields result 2006-10-27T00:18:27-0600 with class of DateTime
date.to_time yields result Fri Oct 27 00:00:00 -0600 2006 with class of Time
time.to_time yields result Fri Oct 27 00:18:27 -0600 2006 with class of Time
date_time.to_time yields result Fri Oct 27 00:00:00 -0600 2006 with class of Time

superclass of DateTime : Date

When to_date is called on an instance of DateTime its still calling it
on Date object since DateTime.superclass == Date. So anywhere a Date is
used, a DateTime can be used.

enjoy,

-jeremy

--
========================================================================
Jeremy Hinegardner jeremy@hinegardner.org

comp.lang.ruby

Time without Date

List Recv

Paul Lutus

List Recv

List Recv

Bil Kleb

List Recv

Paul Lutus

Kevin

Ara.T.Howard

Jeremy Hinegardner

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