Set dynamically hour - DS1307
The numbers you are reporting are very familiar to me.  They are telling me that it is not possible to obtain the time from the RTC chip.

You are getting the time from your server, and as long as the string is actually what you think it is, then the values should be fine.  This snippet works perfecty:

#include &lt;RTClib.h&gt;

char siteData[] = "May 19 2015-09:17:24";

void setup() {
    Serial.begin(115200);

    char *tempDate = strtok(siteData, "-");
    char *tempHour =  strtok(NULL, "-");
    DateTime now(tempDate, tempHour);

    Serial.print(now.year(), DEC);
    Serial.print('/');
    Serial.print(now.month(), DEC);
    Serial.print('/');
    Serial.print(now.day(), DEC);
    Serial.print(' ');
    Serial.print(now.hour(), DEC);
    Serial.print(':');
    Serial.print(now.minute(), DEC);
    Serial.print(':');
    Serial.print(now.second(), DEC);
    Serial.println();
    Serial.println();   
}

void loop() {
}


So it must be in the passing of the data through the RTC chip that is failing.

Check that the chip is actually wired up properly, is running, and is responding normally before you try adding in the code to set the time from the server.