Cross-Platform Calendar App Development

@jastp

Greetings from Logictrix! My name is Jas, and I am looking forward to discuss about your app in details over the Chat or Call. We have enough app developers available in team so I can assure you to deliver this project at a fairly low cost with great quality and with a commitment for long term support. *** We have earned 'Expertise' level in AI development and used many AI platforms like openAI, Freepik, Antigravity, Cursor etc for App development and other AI work! *** We have developed around 400+ Android and iOS apps using Native and Flutter SDK in the past 15 years, Many apps are Live in Google play and App store. We will share our detailed portfolio over the Chat once we connect. Looking forward to your reply... Thanks and Regards Jas

@AwaisChaudhry

As the founder of ZAWN Tech, a full-service IT and Engineering company, I’m fully equipped to tackle your cross-platform calendar app project. Seamlessly integrating Thebox® API into mobile applications is right up my alley. My team and I have extensive experience building REST APIs, ensuring all endpoints perform optimally for event handling like the ones you require. Needless to say, your API credentials will be stored using the most secure storage mechanism available on iOS and Android operating systems. Additionally, from your project description, I’ve clearly understood the challenge of syncing calendars across platforms without compromising data integrity; not to mention preventing duplicates, resolving conflicts effectively, and providing solid offline creation/editing options. My team and I have adeptly handled these issues in numerous projects, implementing robust conflict resolution mechanisms and sophisticated sync engines. Finally, what sets us apart is our interdisciplinary approach. Our skills extend beyond mobile app development - we combine hardware engineering with software development expertise. This has proven invaluable when working on projects involving complex integrations like yours.

@ominfowave

Hello We are Ominfowave Software Services Pvt. Ltd., and we have an expert mobile application development team with 10+ years of experience in building reliable, high-quality apps. ? Our Core Expertise •Android App Development (Kotlin / Native) •iOS App Development •Flutter & FlutterFlow (Cross-platform) Our team understands not just development, but also performance, user experience, scalability, and timely delivery. ? What We Can Deliver ✔ Social media integrations (Facebook, Google, Twitter, etc.) ✔ Google APIs (Maps, Places, FCM, YouTube, Analytics) ✔ Offline & cloud database solutions (SQLite, MySQL, Realtime DB) ✔ Secure payment integrations (Stripe, PayPal, Braintree) ✔ Ad monetization (AdMob, Appodeal, MobVista) ✔ In-App Purchases ✔ Location tracking & real-time features ✔ Chat & messaging applications ? App Types We’ve Built •Social Media Apps •Shopping & eCommerce Apps •Job Portals •Taxi / Carpooling Apps •VPN & Utility Apps •Travel & Booking Apps •Live Streaming Apps •AI & Machine Learning–based Apps ? Why Work With Us •10+ years of hands-on experience •Clean, scalable & secure code • Clear communication & regular updates • On-time delivery with quality assurance • Long-term support after project completion We would love to work with you and build a long-term, trusted business relationship. Let’s discuss your idea and turn it into a successful application Warm regards, Vishal Nasit Ominfowave Software Services Pvt. Ltd.

@diektech

Hi, This is Elias from Miami. I checked your project description and understand you need a mobile calendar app where Thebox® REST API acts as the central company calendar, syncing events with Google, Outlook, iOS, Android, and app-created events. The key part is a reliable sync engine with secure credentials, duplicate prevention, recurrence handling, offline support, and visible sync status. I’ve worked with API integrations, secure mobile storage, and calendar-style sync logic, so I understand the complexity around conflicts, recurring events, and external references. My approach would be to store credentials in Keychain/Keystore, use token/session renewal after first login, normalize all calendar sources into one internal event schema, then sync with Thebox® using external IDs, source metadata, timestamps, and conflict rules. Offline edits would be queued locally and pushed once connectivity returns. I’d be happy to go through the details and suggest the best technical approach. I have a few questions to get a better understanding: Q1 – Will Google and Outlook sync use official OAuth APIs, or only device calendar access? Q2 – Should Thebox® always be the source of truth when conflicts happen? Q3 – Do you need two-way sync for all calendars, or only external calendars → Thebox® in version one? Looking forward to hearing from you.

@Hammadhassan21

Hello You need a secure mobile app that syncs Thebox calendar with Google, Outlook, iOS and Android without duplicates, data conflicts or repeated logins. I will build a centralized sync engine that stores credentials securely using Keychain/Keystore handles OAuth2 for external calendars auto renews sessions, and maps all event data including recurrence attendees metadata into a unified format with unique external IDs. I will implement bidirectional sync using a queue based background service with change tracking timestamps + hashes conflict resolution last write wins or source priority and duplicate prevention via external reference fields. The app will support offline event creation/editing with later sync, attendee invitations via Thebox® user API, and detailed sync logs/status so users always know if events are successfully delivered. Flutter or React Native REST APIs OAuth2 Google/Microsoft iOS EventKit, Android Calendar Provider, secure storage. Result a reliable real time multi calendar system fully centered on Thebox do you prefer strict source priority or flexible last write wins for conflict handling? I can start immediately Let’s discuss. Here You Can Check My Professional Portfolio: https://www.freelancer.com/u/Hammadhassan21 If you find my offer satisfactory, we will be happy to discuss your project in detail. Best Regards Hammad Hassan

@espsofttech

Hi there, I’ve dealt with similar situations where data is coming from multiple sources, and things like duplicate events, missed updates, or conflicts can get messy if not handled properly from the start. What I’d do here is keep the flow simple but reliable. Once the user sets up the API details, we store everything securely and handle login quietly in the background so they don’t have to keep doing it. For syncing, instead of trying to overcomplicate it, I’d run a background process that keeps pulling events from external calendars, aligns them into one structure, and pushes them to Thebox®. Each event will carry a small reference of where it came from — that’s what helps avoid duplicates and makes updates safer. Things like recurring events and attendees will be handled as part of that flow so they don’t break during sync. And if the same event gets changed in two places, we can either keep a simple rule (latest change wins) or adjust based on what you’re more comfortable with. Also, if someone creates or edits something offline, it won’t get lost — it’ll just sync once they’re back online. I’ll keep a small status as well so it’s clear what’s synced and what’s pending. Nothing fancy for the sake of it — just something that works properly when people actually use it daily. Just wanted to quickly check a few things from your side and would request to connect once. Thanks, Rahul A.

@kareemmaize

Hi - the real challenge here is not showing calendar events, it is building a sync engine that can tell exactly where every event came from, what changed, and whether Thebox accepted it. I’d structure the app with secure credential storage, automatic session renewal, local event cache, source metadata, external reference IDs, and a queued sync layer. User connects Thebox - app authenticates silently - pulls Thebox events - reads Google/Outlook/iOS/Android events - maps fields into Thebox format - prevents duplicates using external IDs - syncs creates/updates/deletes - shows delivery status. Looks correct, but fails when recurring events or offline edits overwrite newer changes. Conflict syncing can cause data loss in real use, so I handle it with timestamps, source priority, event hashes, and retry logs. Input - calendar changes. Processing - sync engine + API mapping. Output - consistent Thebox calendar. The part to get right early is duplicate prevention.

@vladang

This looks like a mobile calendar sync system where Thebox® acts as the source-of-truth while Google, Outlook, Apple, and Android calendars behave as external peers. The main challenge isn’t UI—it’s reliable bidirectional synchronization with conflict-safe event mapping. I’d build a sync engine with a normalized internal event model that standardizes all external formats into a single structure before writing to Thebox®. Each event carries an origin tag + external IDs to prevent duplicates across providers. Secure credentials (Keychain/Keystore) are used only for initial handshake; afterwards, a token-based session with silent refresh keeps authentication invisible to the user. Sync runs via background workers with incremental diffing (not full pulls), handling recurring events as rule-based expansions with server-side validation to avoid drift. Conflicts are resolved using “last-write + source priority” rules configurable per calendar. I’ve built similar multi-source sync systems in Bubbl (Nuxt/Express SaaS APIs) where consistency across external APIs was critical under unreliable network conditions. Q1: Should Thebox® always override external calendars or allow bidirectional edits? Q2: Do you want real-time sync or scheduled background intervals (e.g., every 5–15 min)? Q3: Should offline edits queue locally with full conflict reconciliation on reconnect?

@AITSoft

Hi there, I understand you need a cross‑platform calendar app that talks to Thebox® via REST API, supports secure credential storage, automatic login, and robust sync with Google, Outlook, Apple/iOS, and Android calendars. The app will map external events to Thebox® format, keep source metadata, and handle creation, updates, and deletions with conflict resolution and duplicate prevention. I will design a clear sync engine that uses a centralized Thebox® event model, incremental syncing, and a robust offline mode so users can create or edit events offline and sync later. Secure storage will use OS keychains/Keystore, with token-based session renewal and auto-relogin on background tasks. Recurring events will be expanded to Thebox® recurrence rules with proper timezone handling. Attendees will be mapped to Thebox® users, invitations sent via Thebox® API, and external calendar references stored to avoid duplicates. Logs and sync status will show delivery outcomes and error reasons to users. The integration will include a resilient error/retry strategy and comprehensive test coverage to ensure data integrity across all platforms. What would you prefer for the initial MVP: support for Google and Outlook only or include Apple Calendar and Android Calendar from day one? What would you prefer for the initial MVP: support for Google and Outlook only or include Apple Calendar and Android Calendar from day one?

@OutsourceMan

As a part of CnELIndia, I am well-versed in the comprehensive technical requirements necessary for creating a cross-platform calendar app that seamlessly integrates with Thebox® API. With over a decade of experience in mobile app development, particularly in Android and iOS platforms, I possess the necessary skills to ensure that this application functions smoothly on both operating systems. One critical aspect of this project will be maintaining secure storage for user credentials. My team has extensive knowledge of using operating system-specific secure storage mechanisms like Keychain on iOS and Keystore/Secure Storage on Android for maximum security. Additionally, our familiarity with APIs and data syncing across multiple platforms will be invaluable to tackle complex challenges such as recurring events, attendees, duplicate prevention, and conflict resolution. Put simply, my team at CnELIndia brings the right blend of experience, technical expertise, and thorough industry knowledge to undertake this project successfully. I am confident in our ability to create a highly efficient and secure cross-platform calendar app that will integrate smoothly with TheBox® API while facilitating easy sync with external calendars like Google Calendar and Outlook. Let us bring our passion for innovation to your project's forefront!

@mrresearcher99

Hi there, I’ve reviewed your Flutter app requirements and would love to help. With 5+ years of experience in cross-platform development, I specialise in clean UI, smooth performance, and robust API integration. I’ll begin with clear planning, share regular progress updates, and ensure the app is fully tested before launch. Let’s connect to discuss your vision — I’m ready to get started! Best, Bhargav Flutter Developer | Android & iOS Expert

@InterconnectBPO

Hi, We can build this mobile calendar app with a robust sync engine that treats Thebox® API as the central source of truth while seamlessly connecting Google, Outlook, Apple/iOS, and Android calendars. Our approach: Secure credentials: Store API endpoint, username, and password using iOS Keychain / Android Secure Storage. Auto-login & session renewal: Token-based authentication with silent refresh so users stay logged in. Sync engine: Background two-way sync layer that normalizes events from all sources into one internal format, then maps them to Thebox® structure. Duplicate prevention: Use external IDs + source metadata to track origins and avoid duplicate imports. Recurring events: Support RRULE parsing, edits to single instances or full series. Attendees & invitations: Sync attendees and integrate Thebox® user route for internal invites. Conflict resolution: Timestamp/version checks with smart merge rules and user prompts when needed. Offline mode: Queue created/edited events locally and sync automatically once online. Sync visibility: Clear status indicators, logs, retry handling, and delivery confirmations. We have experience building API-driven mobile apps with complex syncing workflows and can deliver a scalable, production-ready solution. We’d be happy to review Thebox® API docs and propose the best architecture. Regards Interconnect Team

@kamran2012

Good to see this project, I will build your cross-platform calendar app with secure credential storage via Keychain/Keystore, automatic session renewal, and a bidirectional sync engine connecting Google, Outlook, Apple, and Android calendars to the Thebox® API. For the sync engine, I will use a last-write-wins strategy with external reference IDs stored per event — each synced event carries its source URI and a hash of its last-known state. On each sync cycle, the app compares hashes to detect changes, resolves conflicts, and queues offline edits for retry once connectivity returns. This prevents duplicates and keeps Thebox® as the single source of truth. Questions: 1) Does the Thebox® API support webhooks for real-time push updates, or will polling be the only option? Looking forward to potentially working together. Thanks, Kamran

@Abhishek2117

Hi, I’m Abhishek Rathore, a senior full-stack/mobile engineer. You need a cross-platform app that securely connects to Thebox® API, auto-authenticates, and reliably syncs events across Google, Outlook, and native calendars without duplication or data loss. I’ll build this as a sync-first system, not just a UI layer. ? Approach React Native (TypeScript) + native modules for calendar access. A background sync engine using a queue-based model (SQLite + job scheduler). Secure storage via iOS Keychain / Android Keystore. Token-based auth with silent refresh. ✅ Core Features • Secure credential storage + automatic session renewal • Bi-directional sync: Thebox® ↔ Google/Outlook/iOS/Android • Recurrence mapping (RRULE parsing + normalization) • Attendees + Thebox® user invitations • Duplicate prevention using external IDs + source tagging • Offline create/edit with deferred sync ☁️ Reliability / Performance Conflict resolution via “last-write + source priority” rules. Delta sync (changed events only) to reduce load. Clear sync logs + per-event status indicators. ? Deliverables Production-ready mobile app (iOS/Android), sync engine, API integration layer, and test coverage. ? Why Me Built similar calendar sync logic in Rhythm (multi-source event aggregation + conflict handling). One question: will Thebox® API support webhooks, or should sync be fully polling-based?

@mobiappsoftware

Hello, I will develop your CALENDAR MOBILE APPLICATION for Android and IOS both platforms with Web admin panel. I am Tulsiram. I have 10 years of experience working as Native and Crossplatform mobile application developer. I am understood your requirements. I am glad if we are working together. If you interested then let's connect. I will provide you Daily updates ,source code after development completed, 1 Year maintenance Support in following Steps: I will available daily 10-12 hours in Working days for you. I will provide you regular updates according to which modules we will decided. After approval each module by you then i will provide your complete source code of your project and will shift on your Domain. Thanks

@alimumtaz112

Hi, It will be an honor for me to work with you. I have got 12 years of mobile application development experience (iOS, android and flutter). Lets discuss this in detail and get this started. Looking forward to hear from you.

@ciss26

Hello, I hope you are doing well. I understand that you are looking to build a CALENDAR MOBILE APPLICATION, and I would be happy to help. I have extensive experience in designing and developing applications and have successfully delivered many projects. What I offer: -Development using the latest technologies -Daily project updates and clear communication -On-time delivery within the agreed timeline -Complete source code provided after project completion -One year of support for the developed work -10+ years of experience in web and app development -Fully responsive, fast-loading, and SEO-friendly design -A powerful super admin panel to manage the entire system Please feel free to initiate a chat so we can discuss your requirements in detail. Thank you and regards, Dheeraj K.

@zainalitariq245

Hey, i will build a cross-platform mobile app integrating Thebox® API with external calendars, enabling secure authentication, automatic sync, event mapping, and seamless bi-directional calendar updates. Professionally, I will implement secure credential storage using Keychain and Keystore, design a robust sync engine handling recurrence, conflict resolution, duplicate prevention, offline sync, and real-time status logs while ensuring smooth API communication and scalability. Do you want real-time sync or interval-based background synchronization for external calendars? https://www.freelancer.pk/u/zainalitariq245 Let’s build a powerful and reliable calendar system that keeps everything perfectly in sync. Best Regards: Zain Ali

@temoberishvili

Hello, This is a solid architecture challenge, and I can help you build a reliable sync layer around your Thebox® API. I’ve worked on calendar integrations and understand the edge cases around recurrence, conflicts, and cross-platform sync. My approach would center on a unified sync engine: Each event (from Google, Outlook, iOS/Android, or Thebox®) is normalized into a common internal model. We store source metadata + external IDs to track origin and prevent duplicates.