I have this compilation error:
TimeSerial.ino:68:29: warning: deprecated conversion from string constant to 'char*' [-Wwrite-strings]
if(Serial.find(TIME_HEADER)) {
^
Please replace this line:
#define TIME_HEADER "T" // Header tag for serial time sync message
with this line:
#define TIME_HEADER 'T' // Header tag for serial time sync message
and compilation goes well.