Select less than the day after the input date by ransack to avoid not include the value of input date.

app-views-_serch_form.haml.rb

.field
  = f.label :created_at
  = f.date_field :created_at_gteq, class: 'datepicker'
  〜
  = f.date_field :created_at_lt_next_day, class: 'datepicker'

config-initializers-ransack.rb

Ransack.configure do |config|
  config.add_predicate 'lt_next_day',
    arel_predicate: 'lt',
    formatter: proc {|v| v.tomorrow.beginning_of_day},
    compounds: false
end

log

  Model Load (1.8ms)  SELECT  `models`.* FROM `models` WHERE (`models`.`created_at` < '2021-06-01 00:00:00') LIMIT 100 OFFSET 0