Why do I get jealous over a girl even though I don't want to be with her at all?

 No, "How old are you today?" and "How old are you?" are not the same in meaning.

"How old are you today?" is a question about the number of years in your age, as of today. It implies that it is your birthday.

"How old are you?" is a more general question about your age, without any reference to today's date. It could be asking about your age at any point in time, past, present, or future.

For example, if someone asks you "How old are you today?", you would answer with your current age. But if someone asks you "How old are you?", you could answer with your age at any point in time, such as your age on your last birthday, your age when you graduated from high school, or your age when you plan to retire.

Here are some examples of how to use each phrase in a sentence:

"How old are you today?"

"Happy birthday! I can't believe you're 30 today."

"How old are you?"

"I'm 27. I'll be 28 on my next birthday."

I hope this helps!