wp-mail.php doesn't account for half-hour and quarter-hour timezones.

[neoscrib]

To reproduce the problem, install Wordpress and set it to post by email. Send a post from an email address which is configured to use a half-hour or quarter-hour timezone (like Afghanistan, +0430).

wp-mail.php calculates the timezone by multiplying the timezone offset by 36. This works fine for whole-hour timezones (Pacific Time -0800, -800 * 36 = -28800 seconds). For half-hour and quarter-hour time zones this does not work (Afghanistan +0430, 430 * 36 = 15480, should be 16200). The reason this happens is because an hour has 60 minutes as opposed to 100 minutes. 430 / 100 = 4.3 hours, not 4.5 hours. 450 * 36 result in 16200 minutes, but timezones are represented as hours and minutes, not fractional hours.

This results in posts that are posted via email from a half-hour or quarter-hour timezone to be posted in the future or in the past from when it was actually posted.

[solarissmoke]

Use strtotime instead of regex parsing

[solarissmoke]

The current logic is replicating what PHP's strtotime() would do internally - I don't see the point. We can just use strtotime, which can handle RFC822 timestamps (including timezone offsets). It doesn't like parenthesised timezone strings (after the +0000 bit), so we should remove those, but otherwise it works for every email header date I've seen.

[neoscrib]

Replying to solarissmoke:

The current logic is replicating what PHP's strtotime() would do internally - I don't see the point. We can just use strtotime, which can handle RFC822 timestamps (including timezone offsets). It doesn't like parenthesised timezone strings (after the +0000 bit), so we should remove those, but otherwise it works for every email header date I've seen.

That makes more sense!

[nacin]

Seems good to me.

[wonderboymusic]

In 34864:

WP Mail: replace logic that was mimicking strtotime() with strtotime(). Without this, the date parsing wasn't accounting for half-hour and quarter-hour timezones.

Props neoscrib, solarissmoke.
Fixes #16993.