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Date: Tue, 8 Nov 2016 13:44:11 +0100
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Subject: Re: [PHP-DEV] DateTime microseconds discussion
From: arjen@parse.nl (Arjen Schol)

Hi Nikita,

The https://3v4l.org/YUhFF example was to demonstrate it is NOT easy to 
set microseconds to zero. NOT to demonstrate new DateTime("5 minutes 
ago") == new DateTime("5 minutes ago").

new DateTime("5 minutes ago, 0 microseconds") indeed sets the 
microseconds to zero (nice to know) but this does not work for 'now'.

See https://3v4l.org/8VE7W for new DateTime('now, 0 microseconds');
And this code fails < 7.1RC4.

Arjen

On 11/08/2016 01:24 PM, Nikita Nefedov wrote:
> Hey Arjen,
>
> On 8 November 2016 at 09:32, Arjen Schol <arjen@parse.nl> wrote:
>> There is no easy way to set microseconds to 0, you have to call setTime
>
> There actually is an easy way, you can pass microseconds absolute value
> in the constructor as well, it would like: `new DateTime("5 minutes ago,
> 0 microseconds")`
>
> As Dan said it is probably a mistkae in the code, really, and it is a
> very popular one,
> to think that `new DateTime("5 minutes ago") == new DateTime("5 minutes
> ago")`.
> If you sample it enough times even on pre-7 versions of PHP you will get
> inequality as well: https://3v4l.org/JV59e (sorry for overloading 3v4l a
> bit here).
> It is especially an undesirable mistake because it causes failures
> randomly,
> no one likes their test suite failing /sometimes/, it makes debugging
> a very unpleasant experience.
>
> When doing date manipulations, let's say the task is to generate a
> report for the
> previous month, you need to always have a base date as a point of
> reference:
>
> ```
> $startDate = new DateTimeImmutable("first day of previous month,
> 00:00:00.0");
> $endDate = $startDate->add(new DateInterval("P1M"));
> ```