I was thinking something like:
```ruby
f.input :starts_at, as: :datepicker, datepicker_opts: {
  min_date: 4.months.ago.to_date, max_date: 1.month.from_now.to_date,
  number_of_months: 5, show_button_panel: true
}
```
With a JS implementation of:
```coffee
$(document).on 'focus', '.datepicker:not(.hasDatepicker)', ->
  defaults = dateFormat: 'yy-mm-dd'
  options = JSON.parse $(@).data 'datepicker-opts'
  $(@).datepicker $.extend(defaults, options)