Ideally, never, unless you are planning for a baby.

Sperm have the capacity to survive inside the reproductive tract for about 5 days. You may indulge into sex during safe period but it is possible that your partner ovulate after few days. Sweetheart, ovulation is the synonym for “unprotected sex,” both of which can result in you being pregnant.

However, from 6th day to the 13th day of your periods are considered as safe period. I suggest you never venture into unprotected sex.