Flight Changi Airport departs from Singapore Changi Airport at 21:50 and arrives at Tokyo Narita International Airport at 05:50.
The flighttime is about 7h 00m. The distance travelled ("as the bird flies"): 4385 Km. So the average speed is roughly 626 Km.
There is an 1 hour time difference between Singapore and Tokyo
The best day to arrive at Singapore is Saturday and it would be best to avoid Wednesday, as prices are on average 83.36% higher than on Saturday. (Average prices, based on 501530 datapoints.)
We have a lot more statistics for flights JL 36 and between Singapore and Tokyo.