Sentosa is part of Singapore, hence the answer would be 0 secs.
it's 1247hr as I'm typing this. But if you are referring to the timezone, it's GMT +08:00.
9:00 PM
Singapore and Perth are both at GMT +8 hours.
I am flying tomorrow with a stop off in Dubai and it takes 7hr20 from Manchester to Dubai and 7hr10 from Dubai to SIngapore (I think).
I think, 5 am(pacific time) ,6 am (mountain time),7 am(central time),8 am(eastern time) and 8:30 am(atlantic time).