makes more sense that the fruit was stolen 13 years ago and not 12
If I'm not wrong Roo stole it in the NW, then they traveled to East Blue, then Luffy eat it, few months after Garp took Luffy to Dandan, Luffy trained 10 years before going to sea, already this should be about 11 years from Roo stealing the fruit, then add 2 years skip it should easily be 13years and few months