かきスタンプ

福岡でフリーランスの物流系のエンジニアやってます。

1月31日の1ヶ月後は何日? 3月31日の1ヶ月前は何日? 各種RDBで確認してみた。

『期限切れとなるのは、登録日より1ヶ月後です』
『1か月前に告知されます』
というのを見た時、「何日だろ?」と思ったのがきっかけ。
   
法的に決められたルールや、国際ルールがあるんかな。
パッとググってみた感じ、見つけきれなかったんで、RDBに聞いてみた。
 
試したのは、以下。

RDBにて、同じ結果となりました。

結果

確認した内容 結果
1/28 の1か月後 2/28
1/29 の1か月後 2/28
1/30 の1か月後 2/28
1/31 の1か月後 2/28
3/28 の1か月前 2/28
3/29 の1か月前 2/28
3/30 の1か月前 2/28
3/31 の1か月前 2/28
1/28 の1か月後(うるう年) 2/28
1/29 の1か月後(うるう年) 2/29
1/30 の1か月後(うるう年) 2/29
1/31 の1か月後(うるう年) 2/29
3/28 の1か月前(うるう年) 2/28
3/29 の1か月前(うるう年) 2/29
3/30 の1か月前(うるう年) 2/29
3/31 の1か月前(うるう年) 2/29

発行したSQL

MySQL

ver:5.7

SELECT
    DATE_ADD(CAST('2018/01/28' AS DATE), INTERVAL 1 MONTH) AS "1/28 の1か月後"
   ,DATE_ADD(CAST('2018/01/29' AS DATE), INTERVAL 1 MONTH) AS "1/29 の1か月後"
   ,DATE_ADD(CAST('2018/01/30' AS DATE), INTERVAL 1 MONTH) AS "1/30 の1か月後"
   ,DATE_ADD(CAST('2018/01/31' AS DATE), INTERVAL 1 MONTH) AS "1/31 の1か月後"

   ,DATE_ADD(CAST('2018/03/28' AS DATE), INTERVAL -1 MONTH) AS "3/28 の1か月前"
   ,DATE_ADD(CAST('2018/03/29' AS DATE), INTERVAL -1 MONTH) AS "3/29 の1か月前"
   ,DATE_ADD(CAST('2018/03/30' AS DATE), INTERVAL -1 MONTH) AS "3/30 の1か月前"
   ,DATE_ADD(CAST('2018/03/31' AS DATE), INTERVAL -1 MONTH) AS "3/31 の1か月前"

   ,DATE_ADD(CAST('2020/01/28' AS DATE), INTERVAL 1 MONTH) AS "2/28 の1か月後(うるう年)"
   ,DATE_ADD(CAST('2020/01/29' AS DATE), INTERVAL 1 MONTH) AS "2/29 の1か月後(うるう年)"
   ,DATE_ADD(CAST('2020/01/30' AS DATE), INTERVAL 1 MONTH) AS "2/30 の1か月後(うるう年)"
   ,DATE_ADD(CAST('2020/01/31' AS DATE), INTERVAL 1 MONTH) AS "2/31 の1か月後(うるう年)"

   ,DATE_ADD(CAST('2020/03/28' AS DATE), INTERVAL -1 MONTH) AS "3/28 の1か月前(うるう年)"
   ,DATE_ADD(CAST('2020/03/29' AS DATE), INTERVAL -1 MONTH) AS "3/29 の1か月前(うるう年)"
   ,DATE_ADD(CAST('2020/03/30' AS DATE), INTERVAL -1 MONTH) AS "3/30 の1か月前(うるう年)"
   ,DATE_ADD(CAST('2020/03/31' AS DATE), INTERVAL -1 MONTH) AS "3/31 の1か月前(うるう年)"

PostgreSQL

ver:9.6

SELECT
    CAST('2018/01/28' AS DATE) + interval '1 months' AS "1/28 の1か月後"
   ,CAST('2018/01/29' AS DATE) + interval '1 months' AS "1/29 の1か月後"
   ,CAST('2018/01/30' AS DATE) + interval '1 months' AS "1/30 の1か月後"
   ,CAST('2018/01/31' AS DATE) + interval '1 months' AS "1/31 の1か月後"
   
   ,CAST('2018/03/28' AS DATE) + interval '-1 months' AS "3/28 の1か月前"
   ,CAST('2018/03/29' AS DATE) + interval '-1 months' AS "3/29 の1か月前"
   ,CAST('2018/03/30' AS DATE) + interval '-1 months' AS "3/30 の1か月前"
   ,CAST('2018/03/31' AS DATE) + interval '-1 months' AS "3/31 の1か月前"   
   
   ,CAST('2020/01/28' AS DATE) + interval '1 months' AS "1/28 の1か月後(うるう年)"
   ,CAST('2020/01/29' AS DATE) + interval '1 months' AS "1/29 の1か月後(うるう年)"
   ,CAST('2020/01/30' AS DATE) + interval '1 months' AS "1/30 の1か月後(うるう年)"
   ,CAST('2020/01/31' AS DATE) + interval '1 months' AS "1/31 の1か月後(うるう年)"
   
   ,CAST('2020/03/28' AS DATE) + interval '-1 months' AS "3/28 の1か月前(うるう年)"
   ,CAST('2020/03/29' AS DATE) + interval '-1 months' AS "3/29 の1か月前(うるう年)"
   ,CAST('2020/03/30' AS DATE) + interval '-1 months' AS "3/30 の1か月前(うるう年)"
   ,CAST('2020/03/31' AS DATE) + interval '-1 months' AS "3/31 の1か月前(うるう年)"

SQL Server

ver:14.0

SELECT
    DATEADD(MONTH, 1, CAST('2018/01/28' AS DATE)) AS "1/28 の1か月後"
   ,DATEADD(MONTH, 1, CAST('2018/01/29' AS DATE)) AS "1/29 の1か月後"
   ,DATEADD(MONTH, 1, CAST('2018/01/30' AS DATE)) AS "1/30 の1か月後"
   ,DATEADD(MONTH, 1, CAST('2018/01/31' AS DATE)) AS "1/31 の1か月後"

   ,DATEADD(MONTH, -1, CAST('2018/03/28' AS DATE)) AS "3/28 の1か月前"
   ,DATEADD(MONTH, -1, CAST('2018/03/29' AS DATE)) AS "3/29 の1か月前"
   ,DATEADD(MONTH, -1, CAST('2018/03/30' AS DATE)) AS "3/30 の1か月前"
   ,DATEADD(MONTH, -1, CAST('2018/03/31' AS DATE)) AS "3/31 の1か月前"

   ,DATEADD(MONTH, 1, CAST('2020/01/28' AS DATE)) AS "1/28 の1か月後(うるう年)"
   ,DATEADD(MONTH, 1, CAST('2020/01/29' AS DATE)) AS "1/29 の1か月後(うるう年)"
   ,DATEADD(MONTH, 1, CAST('2020/01/30' AS DATE)) AS "1/30 の1か月後(うるう年)"
   ,DATEADD(MONTH, 1, CAST('2020/01/31' AS DATE)) AS "1/31 の1か月後(うるう年)"

   ,DATEADD(MONTH, -1, CAST('2020/03/28' AS DATE)) AS "3/28 の1か月前(うるう年)"
   ,DATEADD(MONTH, -1, CAST('2020/03/29' AS DATE)) AS "3/29 の1か月前(うるう年)"
   ,DATEADD(MONTH, -1, CAST('2020/03/30' AS DATE)) AS "3/30 の1か月前(うるう年)"
   ,DATEADD(MONTH, -1, CAST('2020/03/31' AS DATE)) AS "3/31 の1か月前(うるう年)"

Oracle

ver:11g

SELECT
    ADD_MONTHS(TO_DATE('2018/01/28'), 1) AS "1/28 の1か月後"
   ,ADD_MONTHS(TO_DATE('2018/01/29'), 1) AS "1/29 の1か月後"
   ,ADD_MONTHS(TO_DATE('2018/01/30'), 1) AS "1/30 の1か月後"
   ,ADD_MONTHS(TO_DATE('2018/01/31'), 1) AS "1/31 の1か月後"
    
   ,ADD_MONTHS(TO_DATE('2018/03/31'), -1) AS "3/28 の1か月前"
   ,ADD_MONTHS(TO_DATE('2018/03/31'), -1) AS "3/29 の1か月前"
   ,ADD_MONTHS(TO_DATE('2018/03/31'), -1) AS "3/30 の1か月前"
   ,ADD_MONTHS(TO_DATE('2018/03/31'), -1) AS "3/31 の1か月前"
   
   ,ADD_MONTHS(TO_DATE('2020/01/28'), 1) AS "1/28 の1か月後(閏年)"
   ,ADD_MONTHS(TO_DATE('2020/01/29'), 1) AS "1/29 の1か月後(閏年)"
   ,ADD_MONTHS(TO_DATE('2020/01/30'), 1) AS "1/30 の1か月後(閏年)"
   ,ADD_MONTHS(TO_DATE('2020/01/31'), 1) AS "1/31 の1か月後(閏年)"
    
   ,ADD_MONTHS(TO_DATE('2020/03/31'), -1) AS "3/28 の1か月前(閏年)"
   ,ADD_MONTHS(TO_DATE('2020/03/31'), -1) AS "3/29 の1か月前(閏年)"
   ,ADD_MONTHS(TO_DATE('2020/03/31'), -1) AS "3/30 の1か月前(閏年)"
   ,ADD_MONTHS(TO_DATE('2020/03/31'), -1) AS "3/31 の1か月前(閏年)"
FROM 
    DUAL



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