Please be aware that Yogyakarta has multiple airports and that these results are for all airports serving the city.
The best month to fly between Yogyakarta and Banjarmasin is August and the most expensive month to fly is May. (Average prices, based on 2001 datapoints.)
The best day to arrive at Yogyakarta is Wednesday and it would be best to avoid Saturday, as prices are on average 4.8% higher than on Wednesday. (Average prices, based on 601 datapoints.)