Comparison

Monad Calendar Clock vs Celestial Simulation

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

Head to head
About

Monad Calendar Clock

This app visualizes time through planetary and celestial movements, contrasting natural rhythms with mechanical time. It offers unique perspectives on Earth's position in space and time, showing star and planet locations, seasonal changes, and lunar phases.

Highlights
  • Planetary time and date display
  • Celestial ring visualization
  • Heliocentric and Geocentric modes
  • Star and planet location tracking
  • Seasonal and lunar phase progression
  • Twilight and sunrise/sunset times
  • Event scheduling
Features
Read full description

MONAD does something that no other clock or calendar does; it tells the planetary time and date – the solar day, lunar month & seasonal year. MONAD reveals your unique place (and perspective) in planet-centered space and time. MONAD demonstrates the biorhythms of the Earth’s biosphere, and it integrates two types of time: 1) Natural time, which is cyclic, variable, and alive, with 2) Mechanical time, which is linear, highly regular, abstract and artificial. MONAD represents a paradigm shift of planetary proportions; A New Paradigm of Time With MONAD, you see the natural rhythms of time­ proceeding in endless circles and spirals. MONAD shows the location of the stars and planets; what’s visible at night from your location on Earth. MONAD shows the progression of the four seasons and the phases of the Moon; the obliquity of the ecliptic and the Earth’s circle of illumination, and a Twilight Dial tells you the time of Sun rise and Sun set at any latitude and time of year. MONAD shows the agricultural biorhythms of the Earth’s photosynthetic biosphere. MONAD restores the Earth, and the Earth’s biorhythms and biosphere, back to the center of our collective attention and awareness. With MONAD you see the Earth globe from an unusual perspective; the north (or south) polar axial perspective. MONAD automatically places a time zone-spanning Hour Hand at your location on the globe, marking your longitude & latitude, and you see all 24 time zones, all around the globe at the same time, the whole world interconnected. MONAD has four main Modes of operation. Geocentric (Geo) Mode features planet Earth at the center of a time and date-telling, 3-dimensional celestial ring. The algorithms and programming which drive all of the astronomical activity is based on a Sun-centered and highly accurate model of the solar system which you can access in Heliocentric (Helio) Mode. Accelerate through time, into the past or future, and watch how the configuration of the solar system changes. Shift back and forth from Geo to Helio Modes, and it’s easy to see how the two perspectives are related. It’s easy to see how and why the planets have apparent retrograde activity from an Earth-centered perspective. There is so much to explore and learn in MONAD. Astro Mode features a 2-dimensional Calendar-Clock face, which makes it possible to set the time by dragging the hour hand around the dial, or you can set the date by dragging the calendar band, or zodiac band, past the Sun’s meridian or date indicator fixed at noon at the top of the dial. A Table at the top of the screen lists the precise location of the Sun, Moon and planets at any time and date, so basically this Astro screen is equivalent to an astronomy or astrology chart, at any moment in time. Astro Mode will eventually feature a Scientific Astrology Program and an Educational Astronomy Program. Event Mode is where you record and schedule personal events, in the context of important and memorable planetary events we all share. Color-coded Event Wedges are shown in the context of the 4 corners of a solar day (Sun rise, noon, Sun set & midnight), the 4 corners of a lunar month (full and dark Moon, waxing and waning half Moons), and the 4 corners of a seasonal year (equinoxes & solstices). Another unique feature of MONAD is that you can record events “in the Now,” which encourages more presence in your life. A Health Event Mode allows you to see your personal, endocrine biorhythms in the context of planetary biorhythms we all share. The 24 hour circadian Calendar-Clock face is ideally suited to organize and display health events. If you choose to have MONAD integrate with the Apple Health app (HealthKit); then health data (e.g. Sleep period and Steps) read from HealthKit is used for display within the MONAD app. MONAD is beautiful, educational & transformative, and it will change the way you see the world around you, and your place within it. MONAD – A New Paradigm of Time.

About

Celestial Simulation

Features
Read full description

Celestial Simulation Experience the universe as it truly moves. Celestial Simulation is a high-fidelity, physics-based app that lets you explore and understand celestial motion through real simulations—not animations or guesses. Every event is driven by time, location, and real celestial mechanics. From eclipses and planetary motion to lunar occultations and chaotic three-body dynamics, the app turns complex astronomy into intuitive, visual experiences. Observer-Based Simulation Your location matters. Set your observing position on Earth and watch how celestial events change with latitude, longitude, and time. Every simulation adapts instantly to your chosen place and moment. Solar System Geometry Explore the mechanics of the inner solar system: - Annular and hybrid solar eclipses with umbra and antumbra geometry - Planetary conjunctions and minimum angular separations - Mercury and Venus elongations for optimal visibility - Retrograde motion visualized over days and weeks - Transits of Mercury and Venus across the solar disk Most simulations are continuous and time-accurate. Lunar Occultations See how the Moon moves through the sky: - Occultations of bright stars and planets - Local and global visibility bands - Geometry that explains why an event is visible from certain locations Three-Body Dynamics Go beyond classical orbits and explore real gravitational complexity: - Circular Restricted Three-Body Problem (CR3BP) - Lagrange points L1–L5 with stability insights - Chaotic motion in non-rotating frames - Extreme sensitivity to initial conditions - These simulations reveal how real spaceflight dynamics and celestial chaos work. Special Focus: Total Solar Eclipse 2026 (Europe) A total solar eclipse will cross Europe in 2026 — a rare and unforgettable event. Celestial Simulation lets you explore the full path of totality, simulate eclipse geometry from different locations, and understand how timing and position affect what you will see. Use the simulation to: - Compare observing locations across Europe - Visualize eclipse paths and shadow motion - Plan where and when to experience totality Whether you are preparing a journey or simply exploring the mechanics behind the event, the app helps you understand why the eclipse unfolds the way it does. Built for Exploration - Interactive time control - Clean, focused visualizations - Designed for learners, enthusiasts, and curious minds - No clutter, no gimmicks—just the universe in motion Celestial Simulation is a pocket laboratory for understanding how the sky actually works. Whether you’re learning, teaching, or simply fascinated by celestial mechanics, this app lets you see the physics behind the beauty.

Screenshots

Monad Calendar Clock4 screens
Celestial Simulation4 screens

Verdict

The call

The clearest difference is price: Monad Calendar Clock at $0.99 against Celestial Simulation's $3.99. Monad Calendar Clock also leads on iOS requirement (13.0 vs 18.5). On ads, in-app purchases and device support 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

Monad Calendar Clock costs $0.99 and Celestial Simulation $3.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Scorecard2 real differences · 8 level
Monad Calendar Clock versus Celestial Simulation: the parameters behind the verdict, then further details
ParameterMonad Calendar ClockCelestial Simulation
Price$0.99 — better$3.99
Rating3.7 (14 ratings) — better—
Positive reviews22.2% of reviews—
Number of ratings14 — better—
Update frequencyEvery 6 weeks—
AdsNoNo
In-app purchasesNoNo
MonetizationPaid—
DevicesiPhone, iPad, iPod — betteriPhone, iPad
Requires iOS13.0 — better18.5
Further details — not scored
Size266 MB88 MB
Age rating4+4+
DeveloperEarth at the Center LLCDung Le

In-app purchases

None

Monad Calendar Clock

No in-app purchases

None

Celestial Simulation

No in-app purchases

Questions

Is Monad Calendar Clock free?
Monad Calendar Clock costs $0.99, with no in-app purchases.
Is Celestial Simulation free?
Celestial Simulation costs $3.99, with no in-app purchases.
Do Monad Calendar Clock or Celestial Simulation have ads?
Neither Monad Calendar Clock nor Celestial Simulation shows ads.

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