class ActionView::Helpers::DateTimeSelector

def build_year_options(selected, options = {})

"

=> "
build_year_options(1998, start: 1998, end: 2000, year_format: ->year { "Heisei #{ year - 1988 }" })
If year_format option is passed

"

=> "
build_year_options(1998, start: 1998, end: 2000)
If year_format option is not passed
Build select option HTML for year. 
def build_year_options(selected, options = {})
  start = options.delete(:start)
  stop = options.delete(:end)
  step = options.delete(:step)
  select_options = []
  start.step(stop, step) do |value|
    tag_options = { value: value }
    tag_options[:selected] = "selected" if selected == value
    text = year_name(value)
    select_options << content_tag("option", text, tag_options)
  end
  (select_options.join("\n") + "\n").html_safe
end