Refactors date handling with DateService

Replaces DateCalculator with DateService for improved date and time operations, including timezone handling.

This change enhances the calendar's accuracy and flexibility in managing dates, especially concerning timezone configurations.
It also corrects a typo in the `allDay` dataset attribute.

src/index.ts

@@ -3,7 +3,6 @@ import { eventBus } from './core/EventBus';
 import { calendarConfig } from './core/CalendarConfig';
 import { CalendarTypeFactory } from './factories/CalendarTypeFactory';
 import { ManagerFactory } from './factories/ManagerFactory';
-import { DateCalculator } from './utils/DateCalculator';
 import { URLManager } from './utils/URLManager';
 import { CalendarManagers } from './types/ManagerTypes';
 
@@ -40,9 +39,6 @@ async function initializeCalendar(): Promise<void> {
     // Use the singleton calendar configuration
     const config = calendarConfig;
     
-    // Initialize DateCalculator with config first
-    DateCalculator.initialize(config);
-    
     // Initialize the CalendarTypeFactory before creating managers
     CalendarTypeFactory.initialize();