Comparison

Bookends vs Calendar Mirror

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Bookends

Manage your research references and PDFs on your mobile device. Search online databases, import metadata, annotate PDFs, and organize your library. Offers basic functionality for free with optional one-time purchase and yearly subscription for advanced features like cloud sync and unlimited imports.

Highlights
  • Search online reference databases
  • Import metadata and PDFs
  • PDF annotation and markup
  • Barcode scanning for references
  • Cloud sync across devices
  • Share online libraries
  • Create multiple libraries
Features
Read full description

Bookends is the reference management app you've been looking for. The basic version offers: • Search online sites directly (arXiv, Google Books, Google Scholar, JSTOR, the Library of Congress, PubMed, PubMed Central, and Semantic Scholar) or use the built-in browser (EZProxy-compliant) to download reference metadata and PDFs (access privileges required). Searches can return a maximum of 20 references, and only 50 references can be stored in your personal database. • Use unique identifiers such as DOI, PMID, ISBN, or arXiv id to autofill references. • View the text of PDF annotations in a note stream, and create your own with our powerful PDF markup engine. • Barcode scanning, one per day. • And many more features designed to help you discover, organize, and use reference information. Standard, one-time purchase ($14.99): • No limit on searches or importing. Premium, yearly subscription ($14.99). Requires a Standard purchase. • Cloud sync with all your iOS devices and Bookends for Mac (separate purchase). • Share online libraries with colleagues. • Scan documents with Mellel Mobile*. • Create multiple libraries. • Unlimited barcode scanning. • Extract PDF annotations with deep links to annotations and text. • Convenient UI to add PDF notes to the library. • Automate your actions with Shortcuts. * iPad-only. Requires a Mellel Mobile Premium subscription. Subscription is for one year and has an auto-renew option. The subscription can be managed in iOS -> Settings > [your name] > Subscriptions. A subscription will renew if it isn't canceled at least 24 hours before the renewal date. If the subscription is not renewed, Premium will be disabled but Standard will continue to work. Terms of Service: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

About

Calendar Mirror

Features
Read full description

Some calendars you can see but cannot reshare. A subscribed work schedule. A read-only team feed. An account that is not yours. Calendar Mirror makes an editable copy of one calendar inside another calendar you own — one direction only, so the original is never touched. Because the copy lives in your own account, it reaches your other devices on its own. PICK TWO CALENDARS Choose the calendar to copy from and the one to copy into. Add as many pairs as you like; two can share a destination, and anything you add by hand is left alone. Repeating and all-day events, and moved occurrences, all come across. CHOOSE HOW MUCH CROSSES OVER Each pair decides: a full copy; titles and locations only; or "Busy" blocks that show your time and nothing else. Put a label in front of copied titles — "[Work] Standup", or "[Work] Busy" — and carry the meeting link into the copy's notes so a mirrored meeting is one you can join. CHOOSE WHICH EVENTS A pair can skip meetings you declined or have not answered, events the organizer canceled, all-day events and anything marked free, anything shorter or longer than you like, titles containing words you choose, and anything outside a window of the day on the weekdays you pick. Or tag one event at a time: #nomirror, #private, #public in its notes. IT TELLS YOU WHEN SOMETHING BREAKS A healthy pair is silent. If one stops syncing, an all-day warning appears in the destination calendar itself, and clears the moment the pair recovers. ON IPHONE AND IPAD Every pair in one list, with its health and event count. Pull down to sync now. Background refreshes run at the interval you choose, when iOS allows — treat it as the earliest a sync may start, not a guarantee. SEND TIMES "When are you free?" One tap gives you your next three free times as a line of text — "Tue 2–2:30pm, Wed 10–10:30am or Thu 3–3:30pm MDT" — worked out on your device from the calendars you chose, ready to paste into Messages, Mail or Slack. Also a Shortcuts action and a Siri phrase. Nothing leaves your device. ASKWHEN.ME — A SEPARATE PRODUCT YOU CAN TURN ON Off by default; until you turn it on, the app makes no network request of any kind. AskWhen.me is a subscription with its own server: a page at askwhen.me/yourpage where people can ask you for a time. A request page, not a booking page. Your device works out which times to offer and sends only those — never your calendar, your events, your address, or your name beyond the label you choose. Someone picks a time and says who they are; the request comes to your device, and nothing lands in your calendar until you accept. Your device re-checks the time against your real calendar first. Send times can carry a personal link: it opens your page once, for a week, and because you sent it there is no email confirmation — if the time is still clear, your device accepts it for you and they get the calendar file. Free for 90 days, then $19.99 a year; your own name on askwhen.me, or your own domain, are upgrades. Payment is Apple's. The privacy page says what the server holds, and for how long. WHAT IT DOES NOT DO • No scheduling links unless you turn on AskWhen.me, a separate subscription. • No unified calendar view — it makes copies; your calendar app shows them. • No team, admin or SSO features. It is a single-person utility. • Attendees are never copied: Apple's calendar framework cannot set guests. • It cannot sync a calendar your device cannot already see. PRIVACY No account. No analytics, no tracking, no telemetry, no ads. No server, and no network request, until you turn on AskWhen.me — and its server never sees your calendar either. Once a copy lands in iCloud, Google or Exchange, that provider stores it under their policies. Open source under the MIT licence. One purchase covers iPhone, iPad and Mac. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Screenshots

Bookends4 screens
Calendar Mirror4 screens

Verdict

The call

The clearest difference is price: Bookends at Free against Calendar Mirror's $2.99. Calendar Mirror's advantage is in-app purchases (none vs 2) and update cadence (every 3 days vs every 2 months). On ads, device support and iOS requirement there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Bookends is free to download; Calendar Mirror costs $2.99 up front. Bookends sells 2 in-app purchases, starting at $14.99 per year. Calendar Mirror asks for nothing beyond the download.

UpkeepUpdate frequency

Bookends ships an update every 2 months, Calendar Mirror every 3 days. The most recent releases landed on October 16, 2026 and October 11, 2026 respectively.

Scorecard3 real differences · 7 level
Bookends versus Calendar Mirror: the parameters behind the verdict, then further details
ParameterBookendsCalendar Mirror
PriceFree — better$2.99
Rating4.7 (398 ratings) — better—
Positive reviews76.4% of reviews—
Number of ratings398 — better—
Update frequencyEvery 2 monthsEvery 3 days — better
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchases—
DevicesiPhone, iPadiPhone, iPad, Mac — better
Requires iOS18.617.0 — better
Further details — not scored
Size114 MB3 MB
Age rating4+4+
DeveloperSonny Software, LLCMatthew Baylor

Bugs and requests

Bookends

Reported bugs

3 issues
  • Incompatibility with iCloud Optimized Storage
  • Unreliable sync between desktop and mobile versions
  • Occasional data loss or corruption

Requested features

4 requests
  • Nested folders and tags for better organization
  • Automatic PDF metadata extraction
  • Improved search and filtering capabilities
  • Seamless integration with third-party services

Calendar Mirror

Not enough reviews yet to summarise bugs or requests.

In-app purchases

2 purchases

Bookends

Subscriptions1
  • Premium3 Months trial$14.991 Year
One-time1
  • Standard$14.99
None

Calendar Mirror

No in-app purchases

Questions

Is Bookends free?
Bookends is free to download, with in-app purchases available.
Is Calendar Mirror free?
Calendar Mirror costs $2.99, with no in-app purchases.
Do Bookends or Calendar Mirror have ads?
Neither Bookends nor Calendar Mirror shows ads.
Which is updated more often, Bookends or Calendar Mirror?
Bookends ships an update every 2 months, and Calendar Mirror every 3 days. Most recently, Bookends was updated on October 16, 2026 and Calendar Mirror on October 11, 2026.

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