DS1307 real time clock

No problem!

I don't know if this is helpful, but Espruino has NVRAM too. You can use the following functions (at least on the original Espruino board) to access it:

function nvaddr(n) {
  if (n>=0 && n<10) return 0x40006C04+n*4;
  if (n>=10 && n<42) return 0x40006C40+(n-10)*4;
  return 0;
}

// 16 bits, a=0..41
function nvread16(a) {
  return peek16(nvaddr(a));
}

// 16 bits, a=0..41
function nvwrite16(a, value) {
  return poke16(nvaddr(a), value);
}

For instance:

for (var i=0;i<42;i++) nvwrite16(i, i*100)

// then do a hard reset

for (var i=0;i<42;i++) console.log(nvread16(i))
0
100
200
300
...
4000
4100

Obviously you still need a battery to be connected to the board for that though.

(and yes, moving the topic now)