Ethernet W5100 handling of xml files

Projects Networking, Protocols, and Devices
6 
char daysInWord[3];
DayInStr(daysInWord,day_of_week(t.day(), t.month(), t.year()));

Does the DayInStr function only put two characters and a NULL in the array? It must not put more than two, and it MUST put the NULL in order for the string to be passed to a function that expects a string, like client.print().