Should you build your own TimeTac?

Build a self-hosted team time tracking app called Hours. Empty folder, no cloud services.

Stack, no substitutions: Next.js 15 with the App Router and TypeScript, Tailwind for styling, SQLite through Prisma, all data in ./data/hours.db. Session auth with an httpOnly signed cookie, secret in .env as SESSION_SECRET. No third-party auth, no telemetry, no analytics.

Data model: User (name, email, passwordHash, role of admin or member, weeklyHours, vacationDaysPerYear), Project (name, client, archived), TimeEntry (userId, projectId nullable, start, end nullable, note, breakMinutes, approvedAt nullable), Absence (userId, type of vacation or sick or unpaid, startDate, endDate, status of pending or approved or rejected), AuditLog (userId, action, targetType, targetId, before JSON, after JSON, createdAt).

Member views: a big clock in and clock out button showing today's running total, a project picker, an editable list of this week's entries with hour totals per day and week, an absence request form, and a personal balance showing hours worked versus contracted and vacation days used versus remaining.

Admin views: everyone's entries for a chosen month in a grid, one-click approve per user per month which locks those entries from editing, approve or reject absence requests, CRUD for users and projects, and exports: CSV of entries filtered by month and user, plus a printable HTML monthly timesheet per user with signature lines.

Every create, update and delete on TimeEntry and Absence writes an AuditLog row. Never hard delete a TimeEntry, use a deletedAt flag and keep it out of totals.

Rules: overlapping open entries are rejected, entries longer than 12 hours warn on save, a configurable auto break deduction of 30 minutes past 6 hours is applied at display time not at write time.

Out of scope, do not build: mobile apps, GPS or geofencing, payroll integrations, invoicing, multi-tenant orgs, email sending.

Ship a seed script with two users, three projects and a week of sample entries, a README with setup and backup instructions, and Vitest tests for the totals and break deduction math.