The book by that name featuring the poem and many other works of Maya Angelou was published in 1994 (January). As far as when she actually wrote the poem (prior to publishing), probably only Maya herself can tell you. Good luck and I hope this helps!
What year it was written I'm not sure but it was first published in her third volume of poems tilted "And Still I Rise" (1978) that same year it was featured in Cosmopolitan