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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.

Otherwise $geo becomes defacto required by setLocation.

Where the end date must be the day after the start date.

Fix for #67

We need to escape the new line character as well as per RFC : http://tools.ietf.org/html/rfc5545#section-3.3.11