Why doesn't a value update correctly in object and html?

I am making an itinerary generator, all the activities have their duration (in minutes) and the itinerary have a start time so when I generate the itinerary I update the hour in base of activity duration and show the updated hour in the next activity. For example if itinerary start at 6:00 PM and the first activity has a time of 5 minutes, that time will be added to the hour and it will display in the HTML something like:

• 06:00 First activity (5 min)
• 06:05 Second activity (2 min)
• 06:07 Third activity (10 min)

But when update the time, instead of passing it to the next activity it is added to it. For example:

• 06:05 First activity (5 min)
• 06:07 Second activity (2 min)
• 06:17 Third activity (10 min)

Mi code:

Activity Interface:

export interface Activity{
  activityName : string;
  duration     : number;
  zone         : string;
  participants : Participante [];
  time        ?: Date
}

Program component:

export class ProgramComponent {

  program    !: Program[]
  startTime  !: Date; 
  time       !: Date; //It's the time I send and receive from child



  constructor( private gpService: ProgramGeneratorServices ) {
    //I save the start time from Form, don't show all the interfaces 'çause I don't think it's necessary
    this.startTime = this.program[0].startTime;

    this.time = this.programa[0].startTime;
  }

  //This function is only for reset the hour to start, I do two itinerary for 2 weeks so I need restart the hour for ngFor
  resetHour() {
    this.time = this.startTime
  }

  //This function update the hour inside this program component
  updateMinutes( activity?: Activity ) {
    this.time = this.gpService.addMinutes( this.time, activity?.duration);
  }

  //This function update the hour receiving the time from a child component
  updateTime( updatedTime: Date ) {
    this.time = updatedTime;
  }
}

Program html:

<div *ngFor="let subPrograma of programa;"
          class="mb-5"> {{ resetHour() }}

   <div class="my-3">
          <div class="col-6 titulo_seccion ps-2">
            {{ subProgram.sections[1].sectionName | uppercase }}
          </div>
         
//Send the activity data and the time to child and returns the updated time to send to the next activity
          <app-actividad
            *ngFor="let activity of subProgram.sections[1].activities"
            [activity]="activity"
            [time]="time"
            (timeChange)="updateTime($event)"
          ></app-actividad>
   </div>
</div>

Activity app (Child component):

export class ActividadComponent implements OnInit{


  @Input() activity  !: Actividad;
  @Input() time      !: Date;

  @Output() timeChange = new EventEmitter<Date>();

  constructor( private gpService: ProgramGeneratorService ) {
  }

//In OnInit assign time to activity and next to update the time whit a services function
  ngOnInit(): void {
    this.activity.time = this.time;
    this.addMinutes();
  }

  addMinutes(): void {
    this.time = this.gpService.addMinutes( this.time, this.activity.duration);
    this.timeChange.emit( this.time );
  }

}

Activity HTMl (Child)

<div class="row">
  
<div class="col-4">
    <div class="row">
      <div class="col text-start">
        <span> {{ time | date: 'hh:mm' }}
          <span class="cr">
            <span class="point">•</span>
               //THIS is where I print the time
            {{ activity.activityName }} 
                <span *ngIf="activity.time > 0" class="ms-1">
                    ({{ activity.time }} mins)
               </span>
          </span>
        </span>
      </div>

    </div>
  </div>


</div>

Program Generator Services:

export class GeneradorProgramaService {

  constructor( private http: HttpClient ) { }

//This is the function that updates the time
  addMinutes( currentTime: Date, mins: number = 5 ): Date {
    return new Date( currentTime.getTime() + mins * 60000 );
  }
}

Hope someone can help me, I've been stuck for a few hours (If you see something weird is because I omitted code that I think isn't necessary and only put the part related to the problem).

You use time in the HTML and you override time in the addMinutes function in the child component.

...

ngOnInit(): void {
    this.activity.time = this.time;
    this.addMinutes();
}

addMinutes(): void {

 // Here, you override the time. That's why you see the weird one in the HTML.
 this.time = this.gpService.addMinutes( this.time, this.activity.duration);

 this.timeChange.emit( this.time );
}


addMinutes_NoOverride() {

  // Store the new time in a const and then emit it.
  const newTime = this.gpService.addMinutes(this.time, this.activity.duration);

  this.timeChange.emit(newTime);
}