Ovulation-when to have sex

Hi,

My fertile window starts today and goes until the 13th. I ovulate on the 12th. Everyone keeps telling me to do it every second day. Meaning the 8th, 10th and the 12th so we have sex on my ovulation day. However, the app just told me to make sure I have sex on the 11th. Should I stick to the every second day or have sex both on the 11th and 12th?

Thanks for your help.