Populate events: don't set event time zone when it's not specified by Android

            }

            val start = DateTime(tsStart)

            start.timeZone = tz

            tz?.let { start.timeZone = it }

            event.dtStart = DtStart(start)

            when {

                tsEnd != null -> {

                    val end = DateTime(tsEnd)

                    end.timeZone = tz

                    tz?.let { end.timeZone = it }

                    event.dtEnd = DtEnd(end)

                }

                duration != null -> event.duration = Duration(Dur(duration))