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From: Tom Lane <[email protected]>
To: Daniel Gustafsson <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: Ayush Tiwari <[email protected]>
Cc: [email protected]
Subject: Re: to_date()/to_timestamp() silently accept month=0 and day=0
Date: Thu, 23 Apr 2026 11:40:14 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CAJTYsWWNfF+hMpbsTDF8NMr+AuqoDfNxR=oHUZm7xqGP+dJ9rA@mail.gmail.com>
	<[email protected]>
	<[email protected]>

Daniel Gustafsson <[email protected]> writes:
>> On 23 Apr 2026, at 09:57, Michael Paquier <[email protected]> wrote:
>> Perhaps we could consider strengthening such inputs on HEAD once v20
>> opens for business?  It would be really a scary thing to backpatch,
>> still a major release is a different thing.

> This could definitely not be backpatched IMO, a quick check in v14 shows the
> same behaviour.  The gregorian calendar goes from BC1 to AD1 and does not
> define a year 0, to_date('0000','YYYY') correctly returns year 0001, handling
> months/days in the same way at least makes it consistent (though I didn't scour
> the archives to see if it was intentionally done like that).

Looking at the code, I think it intentionally interprets zero as
"missing data".  See for example the stanza at formatting.c:4650ff
where tm_mon and tm_mday can be backfilled from a DDD field.

I'm disinclined to change the behavior around this; you're far
more likely to get complaints than kudos.

			regards, tom lane

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