Some care needs to be taken when soldering the board in place. I created a little jig with an M3 screw, washer and nuts to hold it level and high enough off the board to accommodate the RTC and stay clear of the SMD parts on the Uno.

The second connector on the board (Gnd, 13, Rst) is for a Reset button and/or general push-button in a possible future enclosure.

Yes, the DS1307 is not very accurate.  But it is small!

Note that the shield in the photos (which is does provide access to some pins via the P2/CON1 connector:

…    (10)    (12)    [???]    <- square pad

…    (13)    (11)    (Gnd)    (label end)

But not 5V, and also not in a way I found aesthetically pleasing or amenable to a future enclosure. Hence this wee board  It’s also my first ever manufactured board (EasyEDA). I may never go back to vero board and point-to-point wiring!

The RTC is