feat(calendar): add explained period feature and update translations

src/app/services/translation-service.ts

@@ -221,6 +221,7 @@ export interface AppTranslations {
 		uncompletedStages: string;
 		none: string;
 		currentPlacement: string;
+		explainedPeriod: string;
 		outsideHorizon: string;
 		traceTitle: string;
 		traceLoading: string;