Day One

Private journal with media, location, prompts, and cross-device sync

KINDA · partial replacement
price $4.17/mosubscription / year $50.04estimated build time multi-dayreplaced by 0 people

The visible digital journal loop is buildable, but a credible replacement needs more than the first screen. Day One earns its keep through polish, sync, importers, so expect a weekend or multi-day build and a narrower personal scope.

Build verification: not recorded. How we judge buildability

What you give up

  • conflict-safe multi-device sync
  • mature importers and exporters
  • collaborative editing and sharing
  • native mobile clients

Why people still pay

Day One: People pay for a writing surface they trust for years, plus migration tools, sync, and tiny interaction details that disappear into habit.

Your build guide

The stack, security requirements, and agent rules for a focused replacement.

Before you start

  • Runtime and tools: Swift, SwiftUI/AppKit and SQLite on macOS, with secrets in Keychain where needed.
  • Before starting: A Mac, the current Xcode toolchain and a documented permission checklist; distribution signing is a separate delivery task.
01
Swift, SwiftUI/AppKit and SQLite on macOS, with secrets in Keychain where needed
02
Data design: Store Journal, EntryRevision, Attachment and LocalDate; preserve timezone/date at entry creation and separate a revised entry from its historical timestamps.
03
Setup: A Mac, the current Xcode toolchain and a documented permission checklist; distribution signing is a separate delivery task
engineering roadmap

Implementation plan

1

Phase 1

Pin the working slice and create its example input: Write entries in multiple private journals, attach photos, search text and revisit entries from the same calendar day in earlier years. Confirm setup: A Mac, the current Xcode toolchain and a documented permission checklist; distribution signing is a separate delivery task.

2

Phase 2

Implement persistence and write-time invariants before decorating the UI: Store Journal, EntryRevision, Attachment and LocalDate; preserve timezone/date at entry creation and separate a revised entry from its historical timestamps.

3

Phase 3

Connect the working view to real saved state. Ask for each operating-system permission when its feature is used. Handle denial and revocation without a loop; show permission status and keep local history deletable.

4

Phase 4

Expose the app-specific limits and recovery path in context: SQLite alone does not encrypt a journal. Document the local storage and backup protection honestly; optional encryption must include a tested key-recovery design before being claimed.

5

Phase 5

Walk through this concrete acceptance case and preserve its exported evidence: Write near midnight while traveling, change timezone and browse 'on this day'; the entry stays attached to its chosen journal date and exports with its attachments. Finish the README and backup/restore instructions; report unfinished capabilities explicitly.

the pro prompt
download AGENTS.md
Build the following focused alternative to Day One. This is a deliberately limited personal or small-team substitute, not parity with the paid service.

WORKING SLICE
Write entries in multiple private journals, attach photos, search text and revisit entries from the same calendar day in earlier years.

SETUP AND ARCHITECTURE
Use Swift, SwiftUI/AppKit and SQLite on macOS, with secrets in Keychain where needed. Prerequisites: A Mac, the current Xcode toolchain and a documented permission checklist; distribution signing is a separate delivery task. Before integrating anything, record actual versions and permissions, plus model files or provider limits only where used, in the README; make unavailable dependencies visible rather than simulating success.

DOMAIN MODEL AND INVARIANTS
Store Journal, EntryRevision, Attachment and LocalDate; preserve timezone/date at entry creation and separate a revised entry from its historical timestamps.

IMPLEMENTATION CONTRACT
Ask for each operating-system permission when its feature is used. Handle denial and revocation without a loop; show permission status and keep local history deletable. Provide an input/setup view, the main work view, and a review/export view appropriate to this workflow. Preserve the last saved state if a job or save fails. Include empty, loading, permission-denied, partial and retryable-error states. Log identifiers and error categories without secret values or unnecessary private content.

APP-SPECIFIC BOUNDARY AND RECOVERY
SQLite alone does not encrypt a journal. Document the local storage and backup protection honestly; optional encryption must include a tested key-recovery design before being claimed.

ACCEPTANCE SCENARIO
Write near midnight while traveling, change timezone and browse 'on this day'; the entry stays attached to its chosen journal date and exports with its attachments. Also reopen the app after an interrupted operation, confirm the saved record/export remains inspectable, and document the recovery action. These are implementation acceptance requirements, not a claim that this guide has been tested.

DELIVERY
Deliver a runnable repository with migrations or project-format versioning, a non-sensitive example, environment/permission setup, the exact manual acceptance steps, and a backup/export-and-restore walkthrough. Implement the working slice before optional integrations; list any deferred paid-product capabilities honestly. Do not add capabilities outside the working slice just to resemble the original product.

PROJECT RULES FOR AGENTS.md
Keep the domain invariants above executable at the write boundary. Propose scope changes before adding providers or permissions. Never fabricate source evidence, publish results, identity matches or successful delivery. Preserve user originals and require an explicit confirmation for destructive changes or external publication.

$ open in your agent (prompt prefilled, you press enter), copy the prompt or copy or download AGENTS.md

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Alternatives to building your own

moodiaryA real diary app with media, maps and sync, not a notes app wearing a calendar.1.9kjul 2026open source↗Apple JournalDay One's Apple-shaped core, free because the hardware already collected the money.$0free↗

no votes, no pay-to-list · just what's real

Day One pricing

planmonthlyannual (per mo)what you get
basic$0/user$0/userUnlimited text entries and journals; 1 device; 1 photo/entry; web access, shared journals and exports
silver—$4.17/userUnlimited devices; up to 30 photos/videos per entry; audio/transcription, PDF scans, integrations; 25% print discountAnnual only; billed $49.99/year.
gold—$6.25/userSilver plus reflective AI, daily chat, prompts/summaries/title suggestions/image generation; 35% print discountAnnual only; billed $74.99/year.

free tierUnlimited text entries and journals; 1 device; 1 photo per entry

billingannual only for Silver and Gold; 1-month in-app trial; no public monthly plan

hidden costsGold AI has daily fair-use limits, but Day One does not publish the numbers. Trial eligibility and billing changes are controlled by the original app-store platform.

pricing sources checked 2026-08-13 · pricing source ↗

Questions about Day One

Can you build your own Day One with AI?

Partly. The visible digital journal loop is buildable, but a credible replacement needs more than the first screen. Day One earns its keep through polish, sync, importers, so expect a weekend or multi-day build and a narrower personal scope.

What does the Day One build prompt cover?

The prompt starts with this scope: Write entries in multiple private journals, attach photos, search text and revisit entries from the same calendar day in earlier years. Full-product capabilities excluded from the comparison include: conflict-safe multi-device sync; mature importers and exporters; collaborative editing and sharing. Follow the implementation plan and its prerequisites before expanding the build.

How do I use the prompt, AGENTS.md and agent skills?

Start with the Day One prerequisites and stack, then copy the prompt into your coding agent. Save the project rules as AGENTS.md in the project root. Linked skills are optional packages or source instructions for specific tasks; review their current contents and install only those matching the chosen stack. A skill does not supply API credentials or verify the finished app.

How long will this Day One project take?

The catalogue estimate is multi-day for the limited scope. Setup, integration approvals, debugging, deployment and ongoing maintenance can add time. This is an estimate, not a delivery guarantee.

What would I give up by replacing Day One?

conflict-safe multi-device sync; mature importers and exporters; collaborative editing and sharing; native mobile clients. Day One: People pay for a writing surface they trust for years, plus migration tools, sync, and tiny interaction details that disappear into habit.

What price is this guide comparing against?

The recorded Silver plan is $4.17/mo (annual-equivalent individual subscription), checked 2026-07-31. Check the linked pricing source before buying. Building your own also has hosting, API and maintenance costs; the recorded amount is not a guaranteed saving.

What can I use instead of building Day One?

moodiary: A real diary app with media, maps and sync, not a notes app wearing a calendar. Apple Journal: Day One's Apple-shaped core, free because the hardware already collected the money. Check each option's license, hosting needs and feature limits.

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