Re: New DateTime[Immutable]::createFromTimestamp
| From: | Saki Takamachi | Date: | Sat, 28 Oct 2023 15:47:17 +0000 |
| Subject: | Re: New DateTime[Immutable]::createFromTimestamp | ||
| References: | 1 | Groups: | php.internals |
| Request: | Send a blank email to internals+get-121495@lists.php.net to get a copy of this message | ||
Hi Rowan,
> I'm not sure where you got those numbers; on a 64-bit architecture (surely the vast
> majority of PHP installs), a float can precisely represent any whole number from -2**53 up to 2**53
> - 1. As a Unix timestamp, that's a one-second accuracy for any time 285 million years into the
> past or future.
> https://www.wolframalpha.com/input?i=2**53+as+unix+timestamp
>
> Possibly you're thinking of a representation that counts integers as milliseconds or
> microseconds, instead of seconds?
Yes, I'm assuming a timestamp that includes up to microseconds. This is because in the last
example of the PR description, the microsecond timestamp was expressed as a float.
For information on the number of digits that guarantee float accuracy, please see the following
documentation:
https://www.php.net/manual/en/reserved.constants.php
The constant PHP_FLOAT_DIG is its value. This is set to 16 for IBM and 15 for others.
Regards.
Saki