If `dtEnd` were to be a DateTimeImmutable instead of a DateTime, the add method would have no effect on the outcome.

Here, we update the stored dtEnd with the result of the add method.  For a DateTime object, this will be the same object - for a DateTimeImmutable object, this will be a new DateTimeImmutable one day in the future.

Check if $geo is null before evaluating

Otherwise $geo becomes defacto required by setLocation.

See https://blog.madewithlove.be/post/gitattributes/

Add option for arbitrary time zone string

As long this is an PHP 7 package HHVM cannot be supported any longer.