A day in your light.
Specs don’t sell a wearable. Lived experience does. Here’s exactly what a Tuesday looks like when you’re measuring your light.
Six scenes from a single day
First light
You put on sunscreen and slip on The Gem. You log your application. The Sundial wakes up. Your burn countdown starts: personalized to your skin, your SPF, and the sky outside your window.
The Sundial · Live UVA + UVB
The commute
Twelve minutes outside. It’s cloudy. The Gem doesn’t care. It logs your UVA exposure anyway. By the time you sit down, you’ve accumulated more than you would’ve guessed.
Cumulative exposure
Peak
Lunch outside. The Sundial spikes. Your phone buzzes: “You’re 20 minutes from your burn limit.” You reapply, log it, and the countdown resets.
The Burn · Sunburn window
Errands
A half hour here, twenty minutes there. Each one quiet. All of them counted.
Today’s timeline
Golden hour
Vitamin D. Mood. Circadian rhythm. The app tells you how much sun you’ve gotten today and whether you’re hitting your sun-positive targets (not just your limits).
Sun-positive metrics
The wrap
A daily report. What you absorbed. What you avoided. What your habits are doing to your skin over weeks and months.
Today’s recap + trend line
How a piece of jewelry becomes a sensor.
A photonic sensor measures UVA and UVB intensity from every angle. Bluetooth Low Energy streams it to your phone. The app does the math.
UVA vs UVB
UVB burns. UVA ages. Most products measure one. The Gem measures both.
The Sun Score
Your daily exposure weighted by your skin profile, into one number.
Personalization
Your skin profile is the starting point. Your habits sharpen it.
A nudge, not a nag.
The Gem only notifies you when there’s something you can do about it.
Burn warning: 20 min before your limit
Reapply prompt: when SPF window is closing
Aging check-in: if cumulative UVA spikes
Sun-positive nudge: if under-exposed
The90 · now
You’re 20 min from your burn limit. Consider shade or reapplying.
Is there a subscription or monthly fee?
No. Your Gem comes with the full The90 app and every core feature, with no monthly fee to read your own light. You buy the sensor once.
What does The Gem actually measure?
It reads the UVA and UVB reaching your skin, separately and in real time, then turns the day into a single Sun Score from 0 to 100. Along the way it tracks the light you want, like your morning circadian light and your estimated vitamin D, and the exposure you want to manage, like the UVA that ages your skin.
Do I have to wear it as a necklace?
It comes as a jewelry-grade pendant on a matching gold or silver chain, so you can wear it out of the box. The Gem is also a removable core, so it can move into new ways to wear it as they launch, including a hat clip and bag tag on the way.
How is this different from the UV Index or my weather app?
The UV Index gives one number for a whole city and says the same thing to everyone. The Gem measures the light actually hitting your skin, separates the aging rays from the higher-energy ones, and reads it against your personal skin profile in real time. It is the difference between a forecast and your actual day
Can I wear it in the water?
Rain, sweat, and a quick rinse are all fine. The Gem is water resistant to 1 meter for 30 minutes, so leave it off for the pool, the shower, hot tubs, and saunas.
What if it is not for me?
Try it for 30 days. If it is not right, send it back for a full refund, and every Gem is covered by a 1-year warranty. Free shipping, dispatched from California within 1 to 2 business days, currently within the US.
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