The most relevant question to answer for your jurisdiction is "What is the penalty for lying?"

If none, you were born on March 5, 1957.

(Note on evaluating this: there are some circumstances where the penalty changes later. I know one person who's Global Access paperwork was delayed because they lied to their airline's frequent flyer program about their age. But that was the whole consequence: a need to update their data with the airline).

Whenever Steam's web site asked me for my date of birth before allowing me to view a game trailer, I would punch in January 1, over 10 years after my actual date of birth (still well within grown-ass man territory because I'm geriatric in gamer years). Because they don't fucking need to know exactly when I was born. Only that I'm old enough.