B757-200. THE FLT ATTENDANTS WERE SCHEDULED FOR A 15 HR 38 MIN DUTY DAY; ALL NIGHT; ZZZ2 TURN. THE FLT ATTENDANTS COMPLAINED OF FATIGUE; AND DID NOT HAVE THE OPPORTUNITY FOR ANY REST BREAK.

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RPTED TO WORK ON JUL/WED/03 AT XA10. BOARDED AIRPLANE AT APPROX XA35 AND DEPARTED ZZZ. CAPT DISCOVERED PROB WITH A BATTERY CHARGER AND COMPANY ADVISED A RETURN TO ZZZ1 TO REPAIR. LANDED AT ZZZ1 AT XC04. FLT ATTENDANTS STAYED ON BOARD WITH PAX DURING 2 HR 14 MIN TIME ON GND. DEPARTED ZZZ1 AT XE18; ARRIVING IN ZZZ2 AT XG22. CABIN CLRED WITH LIGHTS ON BRIGHT DURING GND TIME. FLT ATTENDANTS CALLED CREW TRACKING TO QUESTION OUR LEGALITIES FOR CONTINUING HOME TO ZZZ. FLT ATTENDANTS ALL RPTED FEELING VERY TIRED AT THIS POINT. BODY TIME WAS XK00. TRACKING STATED THAT AS LONG AS WE WEREN'T 'SCHEDULED OR RESCHEDULED' TO BE ON DUTY OVER 14 HRS; THAT WE WERE LEGAL. REBOARDED ACFT AT APPROX XH01 AND FLEW TO ZZZ ARRIVING AT ZZZ AT XP18. INCLUDING OUR 30 MIN DEBRIEFING; THIS DUTY DAY WAS 15 HRS 38 MINS. CONSIDERING THE FOLLOWING FACTORS; I STRONGLY BELIEVE THIS TRIP SHOULD HAVE BECOME A LAYOVER FOR THE FLT ATTENDANTS IN ZZZ2: 1) NIGHT FLT. 2) NOT 1 MIN OF TIME AWAY FROM PAX FOR 'REST BREAK' -- GND TIME IN ZZZ1 AND ZZZ2 WAS NOT OUR OWN TIME FOR ANY REST. 3). COMPANY WAS AWARE OF OUR EXTENDED DUTY PERIOD FROM THE TIME WE LEFT ZZZ1 FOR ZZZ2; ALLOWING THEM SUFFICIENT TIME TO REMEDY THE SIT (IE; CANCEL RETURN FLT AND PUT PAX ON ALTERNATE FLTS OR DELAY FLT UNTIL FOLLOWING MORNING; ALLOWING FOR ADEQUATE CREW REST). 4) DUTY DAY WAS SHOWING 15 HRS 38 MINS BEFORE WE REBOARDED ACFT IN ZZZ2. JUST BECAUSE IT'S NOT 'SCHEDULED' THAT WAY DOESN'T CHANGE THE FACT THAT IT'S 'ACTUALLY' GOING TO BE 15 HRS 38 MINS OR MORE. IF ANOTHER INCIDENT OCCURRED (DELAY DUE TO FOG IN ZZZ OR DIVERSION FOR MECHANICAL/EMER) WE WOULD'VE BEEN WAY OVER 16 HR LIMIT. FATIGUE (ESPECIALLY AT NIGHT) LEADS TO ERRORS.