How to create two-dimensional array of Date class for each months (1)

How to create two-dimensional array of Date class for each months:

require 'date'
begin_day = Date.new(2012, 4, 1)
end_day = Date.new(2012, 6, -1)
hash_each_month = (begin_day..end_day).group_by(&:month) # hash
days_each_month = (begin_day..end_day).group_by(&:month).values # two-dimensional array

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