Yes, you run it the first time to set the date/time, and must comment the line out in subsquent builds if you want to retain that original time.
// following lines sets the RTC to a specific date & time.
//RTC.adjust(DateTime("DEC 15 2015","09:58:45"));
// The PCs current time when Arduino code is programmed in.
//RTC.adjust(DateTime(F(__DATE__), F(__TIME__)));
// COMMENT BOTH OUT if actual DS1307/DS3231 times need retaining