My new favorite Apple Watch and Apple Health metric is one that has been quietly working in the background for years. Specifically, it’s a bit of a hidden Apple Watch feature for tracking a great healthy habit: Time in Daylight.

Time in Daylight arrived as a metric in the Health app as part of iOS 17 in 2023. Since watchOS 10, Apple Watch has automatically tracked Time in Daylight just by wearing it.

The feature works by using the watch’s ambient light sensor to measure your environmental brightness. There’s no app to install or tracking mode to enable (though can you optionally disable it).

“Time in Daylight is an estimate of the amount of time spent in sunlight,” Apple explains in the Health app. “When unobstructed, Apple Watch can automatically record an estimated amount of Time in Daylight in Health.”

Because the metric can go as far back as June 2023, you can have years of Time in Daylight data. Time in Daylight data is just populating in your Apple Health app if you’ve been wearing an Apple Watch.

You can check in just a few steps:

• Open the Health app on iPhone or iPad.
• Tap the magnifying glass icon for search.
• Type “daylight” into the search field.

You can also find Time in Daylight from the Mental Wellbeing or Other Data sections from Health Categories on the search page.

Rediscovering this data after multiple years of tracking Time in Daylight minutes and hours has been interesting.

Because spending time in sunlight is a physical and mental health boost, the biggest insight has been quantifying healthy habits that aren’t strictly around exercise.

For example, my highest Time in Daylight day over the last week wasn’t spent walking to the beach or riding my bike over the weekend. Sunday’s outdoor activities rank second.

However, the highest and third highest over the last week were days when I was able to take my MacBook Air outside and write for several hours that netted me more Time in Daylight.

For me, especially as I’m trying to optimize for a consistently positive mood, quantifying Time in Daylight with Apple Watch is a bit of an unlock that I really appreciate right now.

It’s a way to give myself credit for healthy choices in ways that aren’t just reflected in exercise minutes.

Further reading for Apple Watch and Apple Health:

• Apple Watch sleep score became more useful for me with these settings
• Apple at 50: How the company’s shift into health changed my life at 25
• Review: Apple Watch Ultra 3 delivers off-grid connectivity as Series 11 extends battery

You can find the new Apple Watch Series 11 for $329 on Amazon today.