Is the Time object suitable to create a calendar? - ruby-on-rails

Question

I want to make a database-backed calendar. Will the Time object make my life easier? It hasn't so far...
The .end_of_year method gives me some strange information. If it's contemporary time it works flawlessly:
date = '2012-3-2'.to_time(:utc) #=> 2012-03-02 00:00:00 UTC
date.end_of_year #=> 2012-12-31 23:59:59 UTC
However, if you go back in time things get strange.
date = '1399-3-2'.to_time(:utc) #=> 1399-03-02 00:00:00 UTC
date.end_of_year #=> 1399-12-23 23:59:59 UTC
23rd of December? Shouldn't that be 31st?
It's not even consistent:
date = '0000-3-2'.to_time(:utc) #=> 0000-03-02 00:00:00 UTC
date.end_of_year #=> 0001-01-02 23:59:59 UTC
Um, the 2nd of January? OF THE NEXT YEAR? What is going on?
Also, are leap years taken into account by the object?

Answer 1

You could use DateTime instead:
date = '2012-3-2'.to_datetime #=> Fri, 02 Mar 2012 00:00:00 +0000
date.end_of_year #=> Mon, 31 Dec 2012 23:59:59 +0000
date = '1399-3-2'.to_datetime #=> Sun, 02 Mar 1399 00:00:00 +0000
date.end_of_year #=> Wed, 31 Dec 1399 23:59:59 +0000
date = '0000-3-2'.to_datetime #=> Tue, 02 Mar 0000 00:00:00 +0000
date.end_of_year #=> Fri, 31 Dec 0000 23:59:59 +0000
It's mora accurate, and you can format the output

Answer 2

I've did some digging. Here's what I found.
Let's begin with end_of_year:
def end_of_year
change(:month => 12).end_of_month
end
Which relies on change and end_of_month:
def end_of_month
last_day = ::Time.days_in_month(month, year)
last_hour{ days_since(last_day - day) }
end
The most interesting part is happening inside of days_since:
def days_since(days)
advance(:days => days)
end
The advance method is a bit more complex:
def advance(options)
unless options[:weeks].nil?
options[:weeks], partial_weeks = options[:weeks].divmod(1)
options[:days] = options.fetch(:days, 0) + 7 * partial_weeks
end
unless options[:days].nil?
options[:days], partial_days = options[:days].divmod(1)
options[:hours] = options.fetch(:hours, 0) + 24 * partial_days
end
d = to_date.advance(options)
time_advanced_by_date = change(:year => d.year, :month => d.month, :day => d.day)
seconds_to_advance = options.fetch(:seconds, 0) +
options.fetch(:minutes, 0) * 60 +
options.fetch(:hours, 0) * 3600
if seconds_to_advance.zero?
time_advanced_by_date
else
time_advanced_by_date.since(seconds_to_advance)
end
end
And he is the guy we're looking for :
# in rails console
time = '0000-01-01'.to_time(:utc) #=> 0000-01-01 00:00:00 UTC
time.advance(days: 1) #=> 0000-01-04 00:00:00 UTC
time.advance(days: 2) #=> 0000-01-05 00:00:00 UTC
time.advance(days: 3) #=> 0000-01-06 00:00:00 UTC
That's all for now. I will continue to dig.