Yes, yes and yes.
But, ONLY if I instantiate Date object with Today, then ONLY setting the time before converting from UTC to local.
If you're truly only passing the time to your Date object then you're doing it wrong and of course your code will fail. If you instigate that date object with the event date and time then your system clock is NOT relevant. It is the event date that decides whether it converts to BST or GMT
Yes, yes and yes.
But, ONLY if I instantiate Date object with Today, then ONLY setting the time before converting from UTC to local.
If you're truly only passing the time to your Date object then you're doing it wrong and of course your code will fail. If you instigate that date object with the event date and time then your system clock is NOT relevant. It is the event date that decides whether it converts to BST or GMT