My thoughts exactly. I ran the example code and it has the same problem. After about 10-15 minutes it changes the date and time to something incorrect. I tested it on a Diecimilia 328.
Not sure what to do now if the example doesn't work. :-?
// DateTime.pde
// example sketch for the DateTime library
#include <DateTime.h>
#include <DateTimeStrings.h>
#define TIME_MSG_LEN 11 // time sync to PC is HEADER followed by unix time_t as ten ascii digits
#define TIME_HEADER 255 // Header tag for serial time sync message
void setup(){
Serial.begin(19200);
pinMode(13,OUTPUT); // we flash the LED each second
}
void loop(){
unsigned long prevtime;
if( getPCtime()) { // try to get time sync from pc
Serial.print("Clock synced at: ");
Serial.println(DateTime.now(),DEC);
}
if(DateTime.available()) { // update clocks if time has been synced
digitalWrite(13,LOW); // first flash the LED
prevtime = DateTime.now();
while( prevtime == DateTime.now() ) // wait for the second to rollover
;
DateTime.available(); //refresh the Date and time properties
digitalClockDisplay( ); // update digital clock
// send our time to any app at the other end of the serial port
Serial.print( TIME_HEADER,BYTE); // this is the header for the current time
Serial.println(DateTime.now());
digitalWrite(13,HIGH);
}
delay(100);
}
boolean getPCtime() {
// if time sync available from serial port, update time and return true
while(Serial.available() >= TIME_MSG_LEN ){ // time message consists of a header and ten ascii digits
if( Serial.read() == TIME_HEADER ) {
time_t pctime = 0;
for(int i=0; i < TIME_MSG_LEN -1; i++){
char c= Serial.read();
if( c >= '0' && c <= '9'){
pctime = (10 * pctime) + (c - '0') ; // convert digits to a number
}
}
DateTime.sync(pctime); // Sync Arduino clock to the time received on the serial port
return true; // return true if time message received on the serial port
}
}
return false; //if no message return false
}
void digitalClockDisplay(){
// digital clock display of current date and time
Serial.print(DateTime.Hour,DEC);
printDigits(DateTime.Minute);
printDigits(DateTime.Second);
Serial.print(" ");
Serial.print(DateTimeStrings.dayStr(DateTime.DayofWeek));
Serial.print(" ");
Serial.print(DateTimeStrings.monthStr(DateTime.Month));
Serial.print(" ");
Serial.println(DateTime.Day,DEC);
}
void printDigits(byte digits){
// utility function for digital clock display: prints preceding colon and leading 0
Serial.print(":");
if(digits < 10)
Serial.print('0');
Serial.print(digits,DEC);
}