I was hoping the DS1307 would be as accurate as a wristwatch, since the crystal seems similar. I hope the crystal used in the PCB has the load capacitance required by the DS1307 chip (12 pf as I recall).
Since it runs slow, all I could do is put a capacitor in series (not parallel) with the crystal to increase the freq. slightly. Or try a different crystal. Or maybe it cannot be more accurate. But 5 parts in 86000 (seconds per day) isn't so great.