Circadian vs Project Function
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Circadian
Optimize your daily activities by syncing with natural rhythms. This app helps you wake, eat, move, work, and rest at optimal times for improved energy, clarity, and sleep. It leverages sunlight, seasons, and scientific principles to guide your lifestyle for better health.
- Sync daily activities to natural rhythms
- Optimize wake, eat, move, work, and rest times
- Align with sunlight and seasonal patterns
- Seasonal sleep and meal timing calculator
- In-app library on chronobiology and health
- Set reminders for critical circadian events
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THE “WHEN” OF YOUR DAILY ACTIVITIES Feel more energized, think more clearly, and sleep more deeply by syncing your daily life to nature’s rhythm. Circadian helps you wake, eat, move, work, and rest at the optimal times for your body so that you can be at your best. Achieve natural health by honoring your body’s built-in clock. ALIGN WITH SUNLIGHT & SEASONS Start living more in alignment with your local environment. Circadian harnesses daily and seasonal patterns to optimize your days and thus your health. Uncover sunset, sunrise UVA/UVB rise & set as important daily markers and time cues. Entrain your body to the time of day, night, and season for a radically different experience of living. BEDTIME & BIORHYTHM CALCULATOR Plan your optimal hours of sleep with our seasonal sleep calculator. Let your sleep cycles sync to nature’s timing and reap the benefits. Understand why just five minutes of morning light can boost next night's sleep quality by 20%. There is a lot to discover. Everything is connected. EAT & FAST IN SYNC WITH NATURE Research shows that intermittent fasting and early time-restricted eating—eating during daylight hours and fasting after dark—support a healthy metabolism, balanced blood sugar levels, and deeper sleep. Schedule meal and fasting reminders that honor nature’s timing. THE SCIENCE OF CIRCADIAN RHYTHMS Built on Nobel Prize–winning chronobiology, Circadian reveals how light, hormones, and environment shape your well-being. Learn why morning sunlight is crucial for your mood, energy and hormonal balance, how your body needs darkness at night, and why robust rhythms guard against chronic disease. Explore our in-app library for articles and practical tips on melatonin, exercise timing, artificial light, cognition, grounding, and more. With over 800 resources and 1000+ references, Circadian is the ultimate guide for learning about the most important aspect of your health. EVERYDAY BENEFITS ◾ SLEEP WELL – Difficulty falling or staying asleep and excessive sleepiness is often due to chronic circadian disruption. Instead, drift off naturally and wake refreshed. ◾ BALANCE WEIGHT – Circadian disruption is strongly associated with insulin resistance and obesity. Eat and fast in line with nature for an efficient & healthy metabolism. ◾ BOOST ENERGY – Aligning with natural rhythms and increasing exposure to sunlight boosts cellular energy production. ◾LIFT MOOD – Circadian rhythm disruptions and light disturbances are a major hallmark of severe mood disorders. Learn how to produce endorphins, dopamine, and serotonin in your body, naturally. ◾LIVE LONGER – Circadian rhythm disruption plays a direct role in diseases of ageing and ageing itself. The opposite is also true! ◾GET STARTED FOR FREE – Try Circadian for free with no credit card required. START PRIORITIZING WHAT MATTERS MOST ◾Set reminders for critical circadian events essential for health and vitality. ◾Align your lifestyle with the light and dark cycles at your location. ◾Learn the science of circadian rhythms and how to apply it to your daily life. Download Circadian today—and step into a more harmonious and healthier life.
Project Function
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With the Project Function App, you can check in to our facility, manage your membership details, and book appointments. - Access digital membership pass - Book appointments and view session balance - Edit personal information and view membership details - Stay up-to-date with announcements from us! Download the app today! Features connectivity to Apple Watch (synced to HealthKit app)
Screenshots
Verdict
The clearest difference is in-app purchases: Project Function at none against Circadian's 12. Project Function also leads on device support (4 vs 2). Circadian's advantage is iOS requirement (13.4 vs 15.5). On price, update cadence and ads 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
Both are free to download. Circadian sells 12 in-app purchases, starting at $1.99 per month. Project Function asks for nothing beyond the download.
Circadian ships an update every 3 weeks, Project Function every 6 weeks. The most recent releases landed on October 24, 2026 and October 9, 2026 respectively.
| Parameter | Circadian | Project Function |
|---|---|---|
| Price | Free | Free |
| Rating | 4.6 (668 ratings) — better | — |
| Positive reviews | 77.7% of reviews | — |
| Number of ratings | 668 — better | — |
| Update frequency | Every 3 weeks — better | Every 6 weeks |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Free with in-app purchases | — |
| Devices | iPhone, iPod | iPhone, iPad, iPod, Apple Watch — better |
| Requires iOS | 13.4 — better | 15.5 |
| Further details — not scored | ||
| Size | 67 MB | 181 MB |
| Age rating | 4+ | 4+ |
| Developer | Circadian Limited | Project Function LLC |
Bugs and requests
Circadian
Reported bugs
4 issues- Alarms not working properly
- Location and timezone issues
- Crashes and freezes during use
- Notifications not updating with changes
Requested features
5 requests- Customizable alarms and notifications
- Integration with other health/fitness apps
- Historical data tracking and trends
- Personalized recommendations based on user data
- Widget and Apple Watch support
Project Function
Not enough reviews yet to summarise bugs or requests.
In-app purchases
Circadian
- 33% Off Monthly Subscription1 Month trial$1.991 Month
- 10% Off Monthly Subscription1 Month trial$2.491 Month
- Monthly Subscription$2.991 Month
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- 33% Off Yearly Subscription1 Year trial$12.991 Year
- Circadian PLUS (yearly) 40%$14.991 Year
- 10% Off Yearly Subscription1 Year trial$17.991 Year
- Circadian PLUS (yearly) 25%$18.991 Year
- Yearly Subscription$19.991 Year
- Circadian PLUS (yearly)$24.991 Year
- Circadian PRO (Lifetime) 40%$47.99
- Lifetime Purchase - 33% Off$49.99
- Circadian PRO (Lifetime)$79.99
Project Function
No in-app purchases
Questions
Is Circadian free?
Is Project Function free?
Do Circadian or Project Function have ads?
Which is updated more often, Circadian or Project Function?
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