Please be aware that Taipei has multiple airports and that these results are only for Taoyuan International Airport and Hong Kong International Airport.
The best day to arrive at Taipei is Thursday and it would be best to avoid Sunday, as prices are on average 61.13% higher than on Thursday. (Average prices, based on 3246444 datapoints.)
The best time to fly is at around 22. (Average prices, based on 2735 datapoints.)