Is it safe to have unprotected sex during my safe days?

So, I'm just genuinely curious about this. I'm recently interested in using the calendar method (the one where you count your fertile days with a basal thermometer) and I want to know if is safe to have unprotected sex during the days I'm sure I'm not ovulating. Or if my boyfriend still needs to use a condom or other contraceptive method.

Thank you for your replies. 😊😊😊