I had put Zoe down on her playmat on her tummy the other day. She rolled right over by herself within 2 seconds like she had been doing it her whole life! Then later that day I had put her down on her back on her playmat and went to the other room for a second. I heard some fussy noises and went to check her...she had rolled over onto her tummy!
So she rolled both ways for the first time on the same day! Pretty crazy!