There should be a default active record behavior on this I reckon. Querying dates is hard, especially when timezones are involved.
Anyway, I use:
scope :between, ->(start_date=nil, end_date=nil) {
if start_date && end_date
where("#{self.table_name}.created_at BETWEEN :start AND :end", start: start_date.beginning_of_day, end: end_date.end_of_day)
elsif start_date
where("#{self.table_name}.created_at >= ?", start_date.beginning_of_day)
elsif end_date
where("#{self.table_name}.created_at <= ?", end_date.end_of_day)
else
all
end
}