I am not cent % sure since I have not used the DS1307 with PBP. However, at first glance, comparing with the C code I have, it seems you have the SHIFTOUT command configured to MODE= (0)LSBFIRST+CLOCK IDLES LOW. I believe this should be MODE=(1)MSBFIRST+CLOCK IDLES LOW for it to work correctly. Both SHIFTOUT and SHIFTIN should be set to MODE=1

Let us know if this works for you.