maybe AutoFormat in the IDE could improve the indentation? 
2.
readTime() seems to be more complicated than necessary...
a BCD code can be decoded like this: v = (n&0x0f) + 10*(n>>4);
for plausibility checks u could use two arrays with maximum and minimum values: if (v>=vm[i] && v<=vM[i])...
timeDateArray could b an array of bytes (uint8_t) in order to save SRAM space...
3.
the overall structure seems 2 b ok...
i mean: the functions dont look overly long...