Laravel Order通过带时区的日期时间

Question

I'm ordering a list of events by datetime which works fine, however a problem occurs when some items have a timezone applied to them - they don't order correctly. Eg

Event 1 - Ends 20th June 2018 at 15:00:00 (Europe/London)

Event 2 - Ends 20th June 2018 at 13:00:00 (US/Eastern)

When these are ordered by date ascending 'Event 2' shows BEFORE 'Event 1' because timezone is ignored (when in real time it's 2 hours later)

I have tried using a mutator in Laravel to convert both datetimes and timezones to timestamps:

 public function getDatetimeTzSecondsAttribute()
{
    $newDate = new Carbon($this->attributes['date_finish'], $this->attributes['timezone']);

    return $newDate->toTimeString();
}

But understand this won't work as mutators are processed after results have been fetched. I am using pagination for results - whats the best way to order this data via the query builder/eloquent if possible?

Answer 1

If it helps anyone I came up with quite a simple solution after hours of brainache...

Use the MySQL 'CONVERT_TZ' function to change from timezone set to UTC:

->selectRaw('*, CONVERT_TZ(date_finish, timezone, \'UTC\') AS date_finish_converted ')

Then order by the new converted date column (if set) along with the standard date column:

->orderByRaw('COALESCE(date_finish_converted, date_finish), date_finish');

Genius! :)