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Iyola Oyabiyi O.

Personal Project

Chronos Ledger

An offline-first scheduling app for recording commitments, recurring plans, reminders, and conflicts without depending on constant internet access.

Role

Frontend Engineer and Product Builder

Stack

Next.js React TypeScript Dexie Zustand Workbox
Demo

Personal project: Core ownership: Frontend Architecture, Scheduling UX, Local-First Persistence, PWA Behavior

Overview

Chronos Ledger is an offline-first scheduling product built for people who need a dependable record of commitments, not just a lightweight task list.
It is composed of four integrated surfaces: a day-based planner for navigating schedules, timeline and agenda views for reading activities in different formats, an activity editor for creating and updating one-off and recurring entries, and settings and data-management flows for reminders, install behavior, and import/export.

My role and ownership

I led the frontend architecture and implementation of the product, designing and building the day-based scheduling experience from the ground up. I implemented the app shell, timeline and agenda rendering, activity creation and editing flows, recurrence handling, overlap and conflict-resolution interactions, filters, reminder configuration, and import/export workflows. I also set up the local-first persistence model using IndexedDB through Dexie and implemented the installable PWA behavior so the app remains usable offline.

I also structured the product around a single selected day at a time, keeping the scheduling workflow focused while still supporting complex behaviors like recurring activities, edit scopes, and overlap handling.

Key features

  • Day-based navigation with previous and next controls, week strip, and month calendar jump.
  • Timeline and agenda views for reading the same schedule in different ways.
  • Activity editor for one-off and recurring commitments.
  • Conflict detection and guided resolution before saving overlapping entries.
  • Filters by search, status, category, type, and recurrence.
  • Reminder setup, install prompt support, and offline-first PWA behavior.
  • Import, export, backup, and ICS-oriented data portability flows.

Skills demonstrated

  • Frontend engineering: Building a structured Next.js application with reusable UI flows, typed interaction models, and scheduling-heavy interfaces.
  • Product engineering: Translating a scheduling concept into a reliable workflow with day views, recurrence handling, conflict resolution, and reminder setup.
  • Offline-first architecture: Designing around local persistence, installability, and resilient browser behavior instead of assuming constant connectivity.
  • State and data modeling: Managing scheduling data, filters, recurrence rules, and user preferences with predictable client-side flows.
  • System design: Separating planning views, editing flows, settings, and data portability concerns while keeping the product cohesive.
  • Quality engineering: Supporting the codebase with typed models, linting, formatting, and automated testing.

Tech stack

  • Next.js, React, TypeScript
  • Dexie, IndexedDB, Zustand, date-fns
  • Workbox and browser notifications
  • Vitest, Playwright, ESLint, Prettier

Project type

  • Offline-first productivity product
  • Installable PWA + local-first scheduling system