Aerzeit vs SunNow
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Aerzeit
This app analyzes local weather forecasts to suggest optimal times for opening windows to ventilate your home with fresh air. It allows customization of preferred temperature ranges and filters for rain, humidity, wind, air quality, and pollen.
- Optimal window opening times
- Customizable temperature ranges
- Rain, humidity, wind filters
- Air quality and pollen alerts
- 48-hour forecast chart
- Apple Watch companion app
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Aerzeit watches the next 48 hours and tells you the stretches when the air outside is in the temperature range you chose — so you know when it's worth opening up instead of leaving the system running. When nothing in the next two days is worth it, it says so. Everything else is yours to switch on: rain, humidity, wind, air quality, pollen, UV, sun position, and the hours you'd actually consider opening. Set it once for your climate and your house, wherever in the country you are. WHAT IT DOES Pick the outdoor temperature range you'd be happy to let in. Aerzeit watches the local forecast and tells you when conditions match — once a day, at a time you choose. It can also tell you the moment a window opens, and the moment to close it again. Turn on the filters that matter where you live: rain, humidity, wind, air quality, pollen, UV, and the hours of the day you'd actually consider opening up. Set a shortest and longest opening, so you don't hear about gaps too brief to use or leave one open longer than you meant to. A 48-hour chart shows every condition in one place, so you can see where they agree and where they don't. Tap "Use current location" to set a spot to roughly 1 km precision, or search for a town. A companion Apple Watch app and complication show the same at-a-glance status on your wrist, and keep themselves current even when your phone is elsewhere. A Home Screen widget shows the next open-window period at a glance. Aerzeit runs in 50 languages, picked on the Locations page beside °C/°F. WHAT IT DOESN'T DO Aerzeit doesn't model your home — it reports the outdoor conditions and leaves the judgement to you. Opening, sizing and timing the actual airing is yours. It reports public weather and environmental data (including air quality, pollen and UV) as a comfort tool, not medical advice; if a health condition makes any of those matter for you, follow your clinician's guidance. PRIVATE BY DESIGN - Empty Privacy Manifest. The app calls none of Apple's required-reason APIs. - No language detection. Aerzeit never reads your phone's language setting — that's one of the required-reason APIs it avoids — so you pick from 50 languages in the app instead. - Minimal data. To fetch a forecast, the app sends a roughly 7 km grid cell to Aerzeit's server — no account, no identifiers, no raw GPS, no history. Your temperature range and all your filter settings stay on your device. The data export (Settings → Export my data) shows exactly what's held — it's all on your phone. - No accounts. No analytics. No tracking. No advertising. No third-party SDKs beyond a small geospatial maths library. MADE INDEPENDENTLY Aerzeit is built and published by Samuel Harrold, based in Indianapolis, Indiana, USA. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/
SunNow
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# SunNow Product Introduction Have you ever imagined an astronomy model that runs directly on your phone? Without a network connection or cloud computing, you can still know the solar time for your location, when the sun rises, when it sets, and when the moon may be visible. SunNow is exactly that kind of app. It brings the sun, Earth, moon, and your location into one on-device model. Based on latitude, longitude, altitude, date, and time, SunNow calculates sun angle, daylight, twilight, moon phase, and clear-sky radiation locally. You can drag the Earth and moon models to explore how light changes through a day, a month, and a year. In SunNow, time is not just digits on a clock. It becomes the sun's height, the day-night boundary across Earth, the glow before sunrise, the fading light after sunset, and the changing shape of the moon. ## A Sky Inside Your Phone SunNow is not just a weather app or a sunrise lookup tool. It is a local astronomy calculator for daily light, sun, and moon awareness. SunNow uses your current location or a place you select to calculate sun position, local solar time, daylight state, and moon information. You can see whether it is daylight, night, dawn, or dusk, and view sunrise, sunset, and a light curve. These calculations do not depend on the network. With no signal, no mobile data, outdoors, or on a plane, SunNow can still work. ## See Light, Not Just Time We look at time every day, but in real life, light often matters more than the clock. When does the sky begin to brighten? When is the light strongest? How long after sunset can you still see clearly? What phase is the moon in tonight? SunNow turns these questions into something visible. You can check sunrise and sunset, watch the twilight boundary move across Earth, observe clear-sky radiation, and scrub through time. ## Earth, Moon, and Your Location SunNow does not only give you a number. You can drag the Earth model to observe the day-night boundary, switch locations to compare solar states across cities, and save places you care about. The moon is part of the model too. SunNow shows moon phase changes and moon information, helping you see waxing and waning as a continuous process. ## Sunrise and Sunset Alarms For some people, sunrise and sunset are part of a daily rhythm. Regular alarms ring at a fixed clock time, but the sun changes with location and season. SunNow's sunrise and sunset alarms adjust based on your location and date. You can set reminders before sunrise, before sunset, or around specific solar events. For people who live, work, run, travel, photograph, or rest with the sun, this is an alarm that follows the sky. ## Offline, By Design The core features of the current version of SunNow do not require a network connection. Astronomy calculations happen on your device. Your location, saved places, display settings, and alarm rules are stored on your device. The app does not require registration or login, and it does not need to upload your location for its core calculations. You can grant location permission so SunNow can obtain latitude, longitude, and altitude automatically. You can also deny location permission and manually select a place. ## Who SunNow Is For SunNow is for people who care about natural light. It is useful for people living at high latitudes, where daylight length changes dramatically through the year. It helps outdoor workers, early runners, photographers, campers, hikers, commuters, moon watchers, stargazers, and anyone who wants to return their schedule to the sun. If you only want to know when the sun rises today, SunNow can answer that. If you want to understand why the light changes the way it does, SunNow can help you see it. SunNow is an offline astronomy app that uses Earth, the sun, the moon, and your location to show sunrise, sunset, daylight, twilight, moon phases, clear-sky radiation, and solar alarms that adjust with the seasons.
Screenshots
Verdict
The clearest difference is in-app purchases: SunNow at none against Aerzeit's 1. SunNow also leads on iOS requirement (14.0 vs 16.4). On price, ads 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
Both are free to download. Aerzeit sells 1 in-app purchase, starting at $9.99 per year. SunNow asks for nothing beyond the download.
| Parameter | Aerzeit | SunNow |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (1 ratings) — better | — |
| Number of ratings | 1 — better | — |
| Update frequency | Every 5 days | — |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Freemium | — |
| Devices | iPhone, iPad, Apple Watch | iPhone, iPad, iPod |
| Requires iOS | 16.4 | 14.0 — better |
| Further details — not scored | ||
| Size | 27 MB | 96 MB |
| Age rating | 4+ | 4+ |
| Developer | Samuel Harrold | nonono LLC |
In-app purchases
Aerzeit
- Aerzeit Premium$9.991 Year
SunNow
No in-app purchases









