 NASA maintains a catalog of Venus Transits covering the period 2000 BCE to 4000 CE . Currently , transits occur only in June or December ( see table ) and the occurrence of these events slowly drifts , becoming later in the year by about two days every 243 @-@ year cycle . Transits usually occur in pairs , on nearly the same date eight years apart . This is because the length of eight Earth years is almost the same as 13 years on Venus , so every eight years the planets are in roughly the same relative positions . This approximate conjunction usually results in a pair of transits , but it is not precise enough to produce a <unk> , since Venus arrives 22 hours earlier each time . The last transit not to be part of a pair was in <unk> . The next will be in <unk> ; in 2854 ( the second of the <unk> / 2854 pair ) , although Venus will just miss the Sun as seen from the Earth 's equator , a partial transit will be visible from some parts of the southern hemisphere . 
