Concatenate 5 string at once

[system]

I have on serial

There is no serial in that sketch.
Why don't you post the sketch you're trying to debug?

Is this:

char StringFinal[40];
char * sHH;
char * sMM;
char * sSS;

sHH="21";
sMM="43";
sSS="01";

legal C?