Hi druitre,
Have a look at the alembic abcframe intrinsic attribute ;-) that's the same as the “shape instance time” of softimage.
In the meantime if you use timshift please use packed geo and not alembic files ;-)
here's how I manage the time of an alembic file in a “primitive wrangle” (the important bit is the last one)
That's a wrangle that taking a @shapeinstancetime attribute and using that to make random shift of alembic files
float abcfps = chf ("abcfps");
float shapeinstancetime = @shapeinstancetime;
float frame = ( shapeinstancetime + chi ("loopstart") ) % chi ("loop");
setprimintrinsic( geoself(), "abcframe", @primnum, frame/abcfps, "set");