How to use the angular-calendar.CalendarModule function in angular-calendar

import { NgbModule } from '@ng-bootstrap/ng-bootstrap';

import { UtilityModule } from '../utility/utility.module';
import { BookingCalendarComponent } from './bookingCalendar.component';
import { CalendarComponent } from './calendar.component';
import { CalendarService } from './calendar.service';
import * as ac from 'angular-calendar';
import { DateAdapter } from 'angular-calendar';

import 'angular-calendar/css/angular-calendar.css';
import { UIRouterModule } from '@uirouter/angular';

@NgModule({
    imports: [
        NgbModule,
        ac.CalendarModule.forRoot({
            provide: DateAdapter,
            useFactory: adapterFactory,
        }),
        UIRouterModule,
        UtilityModule,
    ],
    declarations: [BookingCalendarComponent, CalendarComponent],
    entryComponents: [CalendarComponent],
    providers: [CalendarService],
})
export class CalendarModule {}