When is your birthday?

So I was born at about 6am, on a Thursday morning, almost 4 decades ago.

I was born during the months when daylight savings is in effect. The country I was born in was the UK. So I was born at about 6am BST, that is about 5am GMT.

I now live in a timezone commonly known as PST, or GMT -8. The practical upshot of this is that when it is 6am BST in the UK, it is 10pm PST of the day before. So, the actual day I was born, it was Wednesday here in California.

Now that I live in California, when is my birthday? Do I take the 24 hours BST from midnight to midnight? Do I take the day that my birth hour falls in? Do I take the calendar day when I was born, even though my birth hour falls outside that day?

Any comments gladly accepted.