The only "safe time" there is to let a man ejaculate into you without making you pregnant is when you're pregnant already. :)
my husband and I were careful for years and years because we didn't want to become pregnant before we were ready. Once I was pregnant, it was such a relief to not have to worry about birth control... We could just get right to it without having to fumble around with things beforehand.
If you don't want a baby right now, don't take the risk. You're playing russian roulette each time you have unprotected sex. There's been more than one woman that's gotten pregnant a day after her cycle, and even *on* her cycle. Use protection every time unless you're okay with getting pregnant. Good luck.