Incorrect DBDate behaviour for years before 100

[sb-relaxt-at]

Affected Version

Framework Version 4, tested on 4.6.0

Description

Constructing certain dates is not working properly with DBDate and DBDatetime.

Steps to Reproduce

$date = new DBDatetime();
$date->setValue(-62135596800);
$date->getValue(); // 1-01-03 00:00:00
$date->rfc2822(); // "2001-01-03 00:00:00"

This is due to this php behaviour:

If the number of the year is specified in a two digit format, the values between 00-69 are mapped to 2000-2069 and 70-99 to 1970-1999.
https://www.php.net/manual/en/function.strtotime.php

Proposed solution

It seems to be sufficient to change DBDate::ISO_DATE to 'yyyy-MM-dd' and the corresponding formats in DBDateTime as well. This should ensure correct four digit rendering (see http://userguide.icu-project.org/formatparse/datetime).

Related issues

This might be related to #9288. And there is another issue when using dates before 1000, see #9133

[robbieaverill]

Thanks for raising this. I see you've referenced the two issues I was going to reference. Do you think this is a different issue to #9133 specifically?

[sb-relaxt-at]

I'm quite confident that it is different but not independent from #9133, as in my example I use a timestamp - which is not handled by the function that causes the issue in #9133. I suppose we can fix this issue which will allow correct creation of year 1 and alike by passing a timestamp. But this won't solve the other issue (passing a date string).