examples/time: fix crash when offset > 0
examples/time: fix crash when offset > 0

this never really worked correctly, i guess.

R=go9p, lucho
CC=go9p
http://codereview.appspot.com/6639059

cleahcim/go9p,lionkov/ninep,henesy/go9p,KevinMGranger/go9p,larsth/go9p,KevinMGranger/go9p,szhilkin/go9p,henesy/go9p,larsth/go9p,floren/go9p,nilium/go9p,nigifabio/go9p,cleahcim/go9p,edahlgren/go9p,szhilkin/go9p,floren/go9p,nilium/go9p,nigifabio/go9p