i would steer clear of tattooing your clean date, but that's just because of my friend matt who has his first date on his left tricep... which isn't his REAL date, but is a daily reminder of what he lost. so yeah.
i have an om on the inside of my left forearm. i got it on my first anniversary. i like it. my sponsee has "faith" on her right wrist. she likes it. tattoos are great.