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https://issues.apache.org/jira/browse/CALCITE-1639?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15971343#comment-15971343
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Julian Hyde commented on CALCITE-1639:
--------------------------------------
Can you please convert this patch to a pull request? It's easier for us to
retain original author, etc.
The Julian epoch (nothing to do with me, BTW!) is the value of the Unix epoch
(Jan 1st 1970) as a Julian date value. It makes it easier to convert from Unix
dates (where Jan 1st 1970 = 0) to Julian dates (where Jan 1st 1970 = 2440588
and Jan 1st 4713 BC = 0). See http://aa.usno.navy.mil/data/docs/JulianDate.php.
PostgreSQL also uses Julian dates internally, BTW.
> timestampadd month should return result month's last day when day part
> overflow
> -------------------------------------------------------------------------------
>
> Key: CALCITE-1639
> URL: https://issues.apache.org/jira/browse/CALCITE-1639
> Project: Calcite
> Issue Type: Bug
> Reporter: hongbin ma
> Assignee: Julian Hyde
> Attachments:
> 0001-CALCITE-1639-deal-with-day-overflow-in-addmonth-with.patch
>
>
> in calcite,
> select timestampadd(MONTH,1,cast('2016-05-31' as timestamp)) will return
> 2016-07-01 00:00:00, and select timestampadd(MONTH,-1,cast('2016-03-31' as
> timestamp)) will return 2016-03-01 00:00:00
> however in mysql, the last day of the next/previous month is always returned:
> {noformat}
> mysql> select timestampadd(MONTH,1,'2016-05-31') ;
> +------------------------------------+
> | timestampadd(MONTH,1,'2016-05-31') |
> +------------------------------------+
> | 2016-06-30 |
> +------------------------------------+
> 1 row in set (0.00 sec)
> mysql> select timestampadd(MONTH,-1,'2016-03-31') ;
> +-------------------------------------+
> | timestampadd(MONTH,-1,'2016-03-31') |
> +-------------------------------------+
> | 2016-02-29 |
> +-------------------------------------+
> 1 row in set (0.00 sec)
> mysql>
> {noformat}
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