Note sure this is the right place to ask this question. Recently I was on a website to buy some flowers to send to a relative. I needed the flowers to reach the person on Feb 3rd. I was ordering from India, it was already Feb 3rd in India. So the "delivery date" tool was greyed out since it was the same day delivery. But I asked my friend in USA to place the order and she could do it. The date was not greyed out since it was only Feb 2nd there in USA...

My question is how does a website determines the time and date of the order? Does it receive that information from the customer's computer? Or IP address's time zone? How does it work? Sorry if this is too elementary ...