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. When nothing in the next two days is worth it, it says so.

The filters below are yours to switch on, for your climate and your house, wherever in the country you are.

WHAT IT DOES

• Your range: pick the outdoor temperature you'd be happy to let in.
• Your filters: rain, humidity, wind, air quality, pollen, UV, sun position, and the hours of the day you'd actually consider opening up.
• Your timing: a shortest and longest opening, so you don't hear about gaps too brief to use or leave a window open longer than you meant to.
• Your alerts: a daily summary at a time you choose, plus, if you like, a reminder the moment a window opens and the moment to close it again.
• A 48-hour chart: every condition in one place, so you can see where they agree and where they don't. Press and hold to read any moment.
• Several locations, each with its own settings. Tap "Use current location", or search for a town.
• A home-screen widget that shows the next open-window period at a glance.
• 50 languages, picked on the Locations page beside °C/°F.

WHEN IT HELPS

• A spring or autumn day when outside is nicer than inside, and you want to know for how long.
• A summer night that cools down enough to let the house breathe.
• A damp spell, when you'd rather air out during the drier hours.
• Pollen season, when you want the windows open only while pollen is below the level you set.

WHAT IT DOESN'T DO

Aerzeit doesn't model your home. It reports the outdoor conditions and leaves the judgment 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

• 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 phone.
• No language detection. Aerzeit doesn't read your phone's language setting; you pick from 50 languages in the app instead.
• Your subscription is checked on your phone. Aerzeit's server never learns who subscribed.
• No accounts. No analytics. No tracking. No advertising. The app's only outside code is Google's Android toolkit, Google Play Billing for the subscription, and a small geospatial math library.

MADE INDEPENDENTLY

Aerzeit is built and published by Samuel Harrold, based in Indianapolis, Indiana, USA.

Samuel Harrold

Additional Information