From: Rajinder Yadav <devguy.ca@...>
Date: 2010-03-03T12:13:52+09:00
Subject: Re: Time, Date and DateTime

Siep Korteling wrote:
> Rajinder Yadav wrote:
>> Hi,
>>
>> I am trying to understand the key differences between Time, Date and
>> DateTime classes.
>>
>> When should one use one over the other? Does anyone know of a good post
>> that explains each of these classes and post on how to do basic time,
>> date arithmetic or conversion between each?
> 
> Note: I am by no means an expert on this.
> 
> Time provides you with a date and a time and is fine if you are sure the 
> date ranges from the year 1970 to 2037.
> It's excellent for timestamps and such. Essentially, it's just the 
> number of seconds elapsed since 1970-1-1. So if the provided methods 
> don't suit you, you have to calculate in seconds, using #to_i and #at .
> 
> Date is a heavyweight, allowing for Julian or Gregorian calendars, 
> specifying the reform dates. You don't have to worry about date ranges 
> (unless you need dates like -5000-1-1). Calculating is superior to Time 
> objects.
> 
> DateTime is the same as a Date with hours, minutes and seconds.
> 
> All three can be enhanced by require-ing active_support.
> 
> The creation of a Date object is about ten times slower than the 
> creation of a time object (on my PC).
> 
> In Ruby 1.9 conversion is simple: #to_date, #to_time and #to_datetime. 
> For versions earlier: google, or copy the 1.9 methods from the 
> documentation (untested).
> 
> hth,
> 
> Siep

Hi Siep,

thank you, this is the kind of background (comparison) info I was 
looking for. The active_support lib really makes date calculation easy.

-- 
Kind Regards,
Rajinder Yadav | http://DevMentor.org | Do Good! - Share Freely