Sun transit date even when it is arctic night

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On SPA.calculateSunriseTransitSet, sun transit is calculated even when there is no sunrise nor sunset and that it is the night (case when the position is inside the Arctic circle).

GregorianCalendar cal = new GregorianCalendar(TimeZone.getTimeZone(ZoneId.of("Europe/Paris"))); cal.set(Calendar.YEAR, 2017); cal.set(Calendar.DAY_OF_YEAR, 01); SPA.calculateSunriseTransitSet(cal, 78., // latitude 16., //Longitude DeltaT.estimate(cal)); // delta T

A simple correction could be to return null for sun transit when : final boolean noDay = (acosArg > 1.0);

Or if this behaviour is correct for you, can we get another method to get information on if there is a day or not.