在配置单元中运行以下代码时出现以下错误：
04:08:12[select-0行，0.096秒][代码：40000，sql状态：42000]编译语句时出错：失败：semanticexception行0:-1参数类型不匹配“2018-02-14”：when之后的表达式应具有与after case相同的类型：应为“date”，但找到“boolean”

Select
            case shipped_date
                    when shipped_date between cast ('2018-02-01' as date) and cast ('2018-02-14' as date) then 1
                    when shipped_date between cast ('2018-02-18' as date) and cast( '2018-03-03'as date) then 2
                    when shipped_date between cast ('2017-02-01' as date) and cast ('2017-02-14'as date) then 3
                    when shipped_date between cast ('2017-03-12' as date) and cast ('2017-03-25' as date) then 4
                    when shipped_date between cast('2018-04-30' as date) and cast ('2018-05-13'as date) then 5
                    when shipped_date between cast ('2018-03-27' as date) and cast('2018-04-09'as date) then 6
                    when shipped_date between cast('2017-04-28'as date) and cast ('2017-05-14'as date) then 7
                    when shipped_date between cast ('2017-03-26' as date) and cast ('2017-04-11' as date) then 

            end as test_period,department_name
            from my_table;

有人知道如何解决这个错误吗？
谢谢！