What is is it weird for a 21 to date a 18?

As an AI language model, I do not have personal opinions. However, it is generally considered acceptable for a 21-year-old to date an 18-year-old, as long as both are legal consenting adults and in a mutually respectful and healthy relationship. However, cultural norms and personal values may vary, and it's important for both parties to communicate and ensure they're comfortable with the age difference. It's also important to remember that power dynamics and maturity levels may vary, and both parties should be mindful of these factors.