Windows Softwares to Built-in Calendar

Sunbird was a standalone calendar application and also a Firefox extension developed by Mozilla, designed for managing events, tasks, and calendar synchronization. It aimed to provide a free and open-source solution for personal and professional scheduling needs.

Visto is a versatile collective task dashboard designed to streamline project management, team collaboration, and workflow automation. It offers a central platform for managing tasks, tracking progress, and improving team efficiency across various business processes.

Holiline Reminder is a free, multi-language calendar and organizer for Windows, designed to help users manage events, deadlines, tasks, and notes efficiently. It includes features like recurring tasks, an address book, and a built-in calendar, offering a straightforward approach to staying organized.

VueMinder Calendar is a comprehensive calendar and task management application for Windows, designed to help users organize their schedules and boost productivity. It offers a wide range of features including robust synchronization options, customizable views, and advanced reminder capabilities, making it suitable for both personal and professional use.

todoyu is a comprehensive web-based collaboration and project management solution designed for teams and businesses of all sizes. It integrates essential tools like task management, time tracking, resource planning, a shared calendar, and client interaction features into a single platform.

Jorte is a comprehensive calendar and organizer application designed to help users manage their schedules, tasks, and notes efficiently across multiple devices. It offers a flexible and customizable interface to suit individual preferences and integrates with popular calendar services.

Kontact is a comprehensive personal information management suite from KDE combining email, contacts, calendar, tasks, and news in one integrated application. It offers robust synchronization options and supports various protocols.

Open365 is a comprehensive, open-source productivity suite offering cloud storage, office applications, and communication tools. Built upon a foundation of open-source technologies like KDE, Seafile, and LibreOffice, it provides a robust alternative to proprietary solutions, emphasizing privacy and control.

Nylas Mail, an extensible open-source email client, offers a unified inbox, robust search, and calendar integration. It supports multiple accounts and provides features like email tracking and undo send, aiming to enhance productivity and email management for users.

EssentialPIM is a versatile personal information manager designed to help you organize your life. It allows you to manage appointments, tasks, notes, contacts, passwords, and more, all within a single, customizable application available for desktop and mobile platforms.

Windows Live Mail was Microsoft's free email client that succeeded Outlook Express and Windows Mail. It offered a familiar interface for managing multiple email accounts, calendars, and contact lists, integrating with other Windows Live services.

Yahoo! Mail is a long-standing web-based email service offering various plans for personal and business use. It provides essential email functionalities along with integrated features like chat and calendar.

Buffer is a comprehensive social media management platform designed to help individuals and businesses schedule posts, analyze performance, and engage with their audience across various social networks.

Lightning is a comprehensive calendar and task management add-on for Mozilla Thunderbird and Seamonkey, designed to integrate seamlessly with email. It offers robust features for scheduling, task tracking, and synchronization with various online calendar services, enhancing productivity directly within your email client.

Microsoft Outlook is a comprehensive personal information manager designed for managing email, contacts, calendars, and tasks.