fix

src/app/app.module.ts

@@ -6,6 +6,8 @@ import { IonicModule, IonicRouteStrategy } from '@ionic/angular';
 import { SplashScreen } from '@ionic-native/splash-screen/ngx';
 import { StatusBar } from '@ionic-native/status-bar/ngx';
 
+import { Calendar } from '@ionic-native/calendar/ngx';
+
 //import { HttpModule } from '@angular/http'
 import { HTTP } from '@ionic-native/http/ngx';
 import { HttpClientModule } from '@angular/common/http'
@@ -22,6 +24,7 @@ import { AppRoutingModule } from './app-routing.module';
   providers: [
     StatusBar,
     SplashScreen,
+    Calendar,
     { provide: RouteReuseStrategy, useClass: IonicRouteStrategy }
   ],
   bootstrap: [AppComponent]