You understand 1 correctly. For 2: [If you were still alive] Today would be your 90th birthday. (Grammatically ok) The first sentence sounds much better than yours, though. It emphasizes that something important has happened. (a death) Birthdays are celebrated by the living. Otherwise we can use a term like ‘anniversary of the date of birth’ For example January 15th is my mom’s birthday. (She is alive.) January 15th was my mom’s birthday. (She is dead.)

Yes, and Yes. You can also say "Today is your 90th birthday". It is her birthday whether or not she is alive.

Yes, let's clarify the nuances of the text: 1. Your Interpretation When you saw the line, you interpreted: - "Today would have been your 90th birthday" as a shorter form of: - "If you had not passed away one year ago, today would have been your 90th birthday." You are absolutely right. The phrase "Today would have been your 90th birthday" is indeed a type of conditional (referred to as the third conditional in English grammar). It implies that if the person's mother were still alive, she would be turning 90 today. The "would have been" indicates something that is contrary to reality (since the mother has already passed away). 2. Using "Today would be your 90th birthday" Let's consider your suggestion: - "Today would be your 90th birthday" as a shorter form of: - "If you were still alive, today would be your 90th birthday." While grammatically correct, there’s a subtle difference between the two phrases: - "Today would have been your 90th birthday" implies that the milestone is impossible because the person is no longer alive. It's commonly used when acknowledging the birthday of someone who has passed away. - "Today would be your 90th birthday" is closer to the second conditional. It suggests a hypothetical present situation, as if imagining that the person were still alive today. This phrasing could sound slightly less natural when talking about someone who has already passed away because it doesn’t fully acknowledge the finality of their passing. Conclusion: The original phrase, "Today would have been your 90th birthday," is more commonly used and feels more appropriate when reflecting on someone who has passed away. It conveys a sense of remembering and honoring the deceased on their special day.

Yes and yes!