Round date in the Array and delete before item - ruby-on-rails

Question

I have an array of DateTime objects like:
a = [
[Tue, 05 Mar 2013],
[Tue, 12 Mar 2013],
[Tue, 19 Mar 2013],
[Tue, 26 Mar 2013],
[Tue, 02 Apr 2013],
[Tue, 09 Apr 2013]
]
where a[0] is a Date object. I need to search for a specific date, like:
a.index('Tue, 06 Mar 2013'.to_date)
to find its index and delete everything before (and in another case after) this item. I need to search by any date, like in the example above, I'm searching by Tue, 05 Mar 2013, so it should be rounded to the nearest value: Tue, 05 Mar 2013. How could it be done in a Ruby way?

Answer 1

Instead of using dates, should be easier to use timestamps:
'Tue, 06 Mar 2013'.to_time.to_i
=> 1362528000
Higher the value, more in the future this date is.
If you are not inserting items in your list frequently, every time you insert a new item, sort it. When you find the index for the date , remove all other items. For example:
# Your dates list converted to timestamps
> times
=> [1362441600, 1363046400, 1363651200, 1364256000, 1364860800, 1365465600]
# Find the timestamp equal or greater than the given date
> correct_index_val = times.find{|x| x <= 'Tue, 27 Mar 2013'.to_time.to_i}
=> 1362441600 # this is actually the position for 26 Mar
# Position of the value equal or greater than the given date
> times.index(correct_index_val)
=> 3
# cutting the array in that point
> times[idx..-1]
=> [1364256000, 1364860800, 1365465600]

Answer 2

Here is the way :
I need to search it for specific date.
require 'date'
a = [
['Tue, 05 Mar 2013'],
['Tue, 12 Mar 2013'],
['Tue, 19 Mar 2013'],
['Tue, 26 Mar 2013'],
['Tue, 02 Apr 2013'],
['Tue, 09 Apr 2013']
]
nwar = a.flatten.map{|d| Date.parse(d)}
# point free style is - a.flatten.map(&Date.method(:parse))
srchdt = Date.parse('Tue, 06 Mar 2013')
p nwar.index(srchdt) # => nil
srchdt = Date.parse('Tue, 26 Mar 2013')
p nwar.index(srchdt) # => 3
After we have index of the item, I need to delete everything before (another case is to delete after) this item.
ind = nwar.index(srchdt) # => 3
nwar.shift(ind)
p nwar.map(&:to_s) # => ["2013-03-26", "2013-04-02", "2013-04-09"]