Appointments+ does not handle changes to/from daylight savings

With the transition from Eastern Daylight Time (EDT) to Eastern Standard Time (EST) as part of Daylight Savings (DST), the appoinmtents+ plugin is messing up appointments booked before the DST change because the plugin assumes that a day always will be 86400 seconds long, as demonstrated from the following code snippet.

$time = strtotime( $date, $appointments->local_time ) + ($add * 7 * 86400) ;

In most of the Western world, that is an incorrect assumption, twice per year when we transition to/from Daylights Savings Time.

Although it's a (little bit of a) challenge on installs using PHP versions prior to v5.3, a simple way to not have to worry about DST is implementing the DateTime() functionality. It automatically manages DST changes (assuming the code then uses intervals, i.e. + 1 week or +1 day).