# Circadian Rhythm & Sleep: ARC — Energy, Sleep & Caffeine Timer > Circadian rhythm tracker for personalized energy, sleep, and focus optimization. (iPhone/iPad app by Pritam Ghosh.) - Source: https://appshunter.io/ios/app/circadian-rhythm-and-sleep-arc/id6758214892 (this page in markdown: same URL + `.md`) - Developer: [Pritam Ghosh](https://appshunter.io/developer/1871515469) - Category: Health & Fitness, Productivity - Price: Free with in-app purchases - Rating: 4.29/5 from 7 App Store ratings · 4 written reviews indexed - Age rating: 4+ - Requires: iOS 15.1 · 49 MB - Languages: English - Released: 2026-02-05 - Data updated: 2026-08-23 - Monetization: free with in-app purchases - User reviews in markdown: https://appshunter.io/ios/app/circadian-rhythm-and-sleep-arc/id6758214892/reviews.md ## What is Circadian Rhythm & Sleep? Your body already knows when to sleep. ARC helps you hear it. THE LIVE CAFFEINE FORECAST NO OTHER APP HAS Log your morning espresso. Watch the 12-hour decay curve update in real time on your home screen. See your mg level rise and fall hour by hour, with a clear sleep-safe threshold line. Know the precise minute it's safe to sleep tonight. Most people are sabotaging their sleep every single day — and don't know it. WHO ARE YOU? Lion. Bear. Wolf. Dolphin. ARC's chronotype diagnosis identifies your biological wiring — the reason mornings feel impossible, or why you come alive at 10 PM. Then it builds your entire day around it. Built for the 73% who don't fit a generic 9-to-5 — including night owls, DSPD, and shift workers. YOUR DAILY PROTOCOL ARC's home screen shows you one thing: what to do right now. SUNLIGHT TIMER Track morning light exposure toward your 20-minute target. Sets your cortisol rhythm for the next 16 hours. LIVE CAFFEINE FORECAST Log every drink. Watch the 12-hour decay curve. Know your wall — the last safe coffee before it starts cutting your deep sleep. PEAK FOCUS WINDOWS Your hardest work, scheduled at your chronotype's natural cognitive peak. WIND-DOWN SEQUENCE Melatonin begins 14–16 hours after your cortisol peak. ARC times the signal so you don't have to think about it. NUDGES THAT KNOW WHO YOU ARE Wolves get notifications written for late-night focus. Lions get protocols built for early bedtimes. Night-shift workers get the entire schedule inverted. No two chronotypes get the same nudges. "Wolves hit their real peak at 6 PM. Use this window for your hardest work." "Caffeine wall — every cup after this costs you 15-20 minutes of deep sleep." "Start winding down — your delayed melatonin needs the signal early." Written for your chronotype. Never generic, never annoying. BUILT ON REAL SCIENCE Based on protocols from Dr. Andrew Huberman (Stanford) and Dr. Matthew Walker (UC Berkeley). Circadian rhythm research won the Nobel Prize in 2017. Your internal clock controls everything — when you're sharp, when you crash, when you should sleep. Try ARC Pro, Cancel anytime before your trial ends and you won't be charged. SUBSCRIPTION PRICING ARC Pro is available as: • Weekly: $4.99/week • Monthly: $9.99/month • Annual: $39.99/year (Best Value — Save 86% vs weekly) Payment will be charged to your Apple ID account at confirmation of purchase. Subscription automatically renews unless canceled at least 24 hours before the end of the current period. Manage or cancel anytime in your App Store account settings. Privacy Policy: https://www.notion.so/Privacy-Policy-for-ARC-Sync-Your-Life-2f2af72016c9802bace6fddd4a1ed526 Terms of Service: https://www.notion.so/Terms-of-Service-for-ARC-Sync-Your-Life-2f2af72016c980c8be7be0bacf1ee076 ## Key features - 15-Point Precision Diagnosis - Bio-Diagnosis for Chronotype - Circadian Compass energy map - Caffeine Half-Life Tracker - Photon Latency Nudges - Energy-Based Mission Scheduling ## Pricing and in-app purchases Base price: Free. **Subscriptions** | Subscription | Price | Period | | --- | --- | --- | | ARC Yearly Pro | $39.99 | per year | | ARC Monthly Pro | $12.99 | per month | | ARC Weekly Pro | $4.99 | per 7 days | ## Recent user reviews (4 of 4) All indexed reviews: https://appshunter.io/ios/app/circadian-rhythm-and-sleep-arc/id6758214892/reviews.md ### 1/5 — Very strong subscription binding! *2026-06-05* The autumn application strongly imposes its paid Subscription, which has a very negative impact on the experience of using the application. ### 5/5 — 5 Stars for Potential *2026-04-12* I’m giving this five stars for potential and because it serves a niche in the market that is very much needed. However, it is a bit off for me. I’m a wolf type. Already knew that. Being a wolf type my lifestyle is already built around my DSPD so my schedule does not configure to your typical 9-5. That being said, the app quiz still forced me to answer questions about peak energy and coffee timing based on a 9 to 5 schedule. I thought the whole idea of this app was that I would not have to answer questions as though I have a typical schedule. So for some reason, it thinks I have my first coffee at 3:30 AM, which is an hour before I told it I usually go to sleep. Seems like a bug? I also would like the ability to switch from UK (military) time to U.S. time. **Developer response:** You're 100% right, and we fixed all three. The 3:30 AM coffee bug was a hardcoded "AM" that ignored your actual wake time. The quiz now uses relative timing ("a few hours after waking") instead of fixed clock times. And we've added a 12h/24h toggle in Settings. Rolling out in the next few hours. Thanks for flagging these. Wolves with DSPD are exactly who ARC should serve best. ### 5/5 — Know your body! *2026-02-17* I must say I didn’t pay much attention to my circadian rhythm but it’s nice to know about how my body works and also what the optimal time it is to drink coffee and when to cut it off so it doesn’t affect my sleep. It’s a good little reminder to help stay in tune with your body! **Developer response:** Really glad that it helped you in your busy life. Keep your circadian rhythms healthy and enjoy ✌️ ### 5/5 — Essential for a night shifter *2026-02-07* As a night shifter trying to stay consistent has its ups and downs, where this maps out your day, when you shouldn’t have anymore caffeine and such to try and optimize your circadian rhythm. This isn’t JUST for night shifters and it’s for everyone. Even if you are on a standard 9-5. It helps people create better habits for longevity of a circadian rhythm. **Developer response:** Thank you so much for this so positive review ## Frequently asked questions about Circadian Rhythm & Sleep ### What is ARC's subscription pricing? ARC Pro offers weekly at $3.99, monthly at $9.99, and yearly at $29.99. The yearly plan provides the best value, saving users 75%. ### Does ARC offer a free trial? Yes, all ARC subscription plans include a 3-day free trial. You can manage your subscription and cancellation through your App Store account settings. ### How does ARC diagnose my chronotype? ARC uses a 15-point precision diagnosis during onboarding, asking specific questions to calibrate your rhythm with medical-grade accuracy and identify if you are a Lion, Bear, Wolf, or Dolphin chronotype. ### What are the science-backed results users can expect from ARC? Users can expect to eliminate the afternoon energy crash, fall asleep faster by timing wind-down routines, and achieve states of deep flow by working with their brain chemistry. ### On which devices can I use ARC? ARC is supported on iPhone, iPad, and iPod devices, making it accessible across the Apple ecosystem. ### How often is ARC updated? The latest version of ARC is 1.2.0, and it was last updated on March 15, 2026. This indicates a commitment to ongoing development and improvements. ### What is the age rating for ARC? ARC has an age rating of 4+, making it suitable for a wide range of users interested in health and wellness. ### Does ARC have ads? No, ARC does not contain advertisements. The app is free to download and offers in-app purchases for its Pro features. ## Version history (last 5 releases) ### 1.8.0 — 2026-07-07 A calmer, clearer ARC. We rebuilt the app around one idea: tell you the one thing to do right now — and get out of the way. • Redesigned Home — a single focused view with a live countdown ring showing exactly what your body needs this moment. No more cluttered dashboard. • One-tap check-ins — log your energy or sleep in a single tap. ARC does the work; you just confirm. • New Progress tab — see how in-sync you're getting in plain language, with the deep charts one tap away when you want them. • Smarter & simpler — we streamlined the app to three focused tabs, and the science now shows up right where you need it. • Smoother everywhere — faster, cleaner, and more reliable. Wake with your biology, not against it. ### 1.7.0 — 2026-06-12 AI Morning Debrief ARC now reads your logged caffeine, sunlight, sleep, and energy data and gives you a 2–3 sentence personal insight each morning — plus one specific action for today. Why Am I Tired? — On-Demand AI Diagnosis Log a low energy check-in and ARC now tells you the most likely cause from your data — whether it's caffeine timing, poor sleep, or a sunlight gap — and gives you one fix for right now. Smarter Home Screen The morning debrief hides automatically after 2pm so your home screen always feels relevant to the time of day. Bug fixes and performance improvements. ### 1.5.8 — 2026-05-18 This update brings visual refinements and UI polish across the app. • Refined onboarding flow with cleaner layouts and tighter copy • Updated paywall design • Caffeine forecast visualization on the home screen • Smoother animations and small fixes throughout Thanks for the reviews — keep them coming. ### 1.5.6 — 2026-05-10 What's new: • Live caffeine forecast on Home — watch your levels decay over the next 12 hours, with a clear sleep-safe threshold line. • 12h / 24h time format toggle — for everyone who didn't want their wake time written as 02:00. • Onboarding rebuilt for Wolves, DSPD, and night-shift workers. Less 9-to-5 bias, sharper insights. • Resume mid-quiz if you got interrupted by a call. Bug fixes — including the 3:30 AM coffee time some Wolves were seeing. Keep the reviews coming. ### 1.2.0 — 2026-03-15 What's New in ARC v1.2.0: - Critical Caffeine Wall Alert: New biological deadline detection. The app now specifically warns you when you've hit your 'Caffeine Wall' with a high-visibility alert to protect your deep sleep recovery. - Synchronized Biometrics: We've perfectly aligned our notification engine with the in-app countdowns. Your biological nudges and the UI are now in 1:1 sync. - Optimized Hero Card: A redesigned, simplified home screen interface that puts your most critical biological goal front and center with improved visual hierarchy. - Bio-Anchor Tracking: Improved one-tap sunlight logging to anchor your circadian rhythm and build your biological baseline. - Real Data Insights: Bio Analysis charts are now fully dynamic, reflecting your actual sunlight latency and wake stability over the last 7 days. - Architecture Cleanup: Massive under-the-hood optimization, removing unused dependencies for a lighter, faster application experience. ## More apps by Pritam Ghosh - [GoodFriend: Stay In Touch](https://appshunter.io/ios/app/goodfriend-stay-in-touch/id6758581803) - [Pick One: Decision Maker](https://appshunter.io/ios/app/pick-one-decision-maker/id6759740295) - [CleanLabel: AI Food Scanner](https://appshunter.io/ios/app/cleanlabel-ai-food-scanner/id6760940713) - [Forge: Iron Mind & Discipline](https://appshunter.io/ios/app/forge-iron-mind-and-discipline/id6767904744) - [Daily 3 Habit Tracker: Pip](https://appshunter.io/ios/app/daily-3-habit-tracker-pip/id6782576366) All apps by Pritam Ghosh: https://appshunter.io/developer/1871515469 --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-23.*