What Is Solar-Based Scheduling for Mac Appearance?

Why Fixed-Time Schedules Don't Work Year-Round

The most common way people configure dark mode on Mac is to set it to activate at a fixed time - say, 6:00pm every day. It feels sensible. But the problem reveals itself almost immediately: the clock never changes, and the sun never agrees with it.

In summer at high latitudes, sunset can fall as late as 9:00–10:00pm. If dark mode activates at 6pm, your Mac is displaying a dark interface for three to four hours while your room is still flooded with afternoon light. The opposite problem strikes in winter: sunset at 3:54pm in London (51°N) means dark mode at 6pm arrives more than two hours after the sun has already gone down.

That London figure is not an isolated edge case. At 51°N, sunset ranges from 3:54pm in December to 9:21pm in June - a swing of more than five and a half hours. A fixed 6pm schedule is wrong by multiple hours for large portions of the year. At higher latitudes - Oslo, Helsinki, Anchorage - the swing is even more extreme.

Fixed-time schedules also fail silently. Because the mismatch creeps in gradually over weeks, most users never connect the dots. They just use dark mode when it's light outside in summer and wonder why their eyes feel tired in winter evenings when the screen is still in light mode. Solar scheduling eliminates the problem entirely. The switch time adjusts automatically every single day to stay in lockstep with actual sunrise and sunset.

How Solar Scheduling Works on Mac

Solar scheduling does not require constant GPS polling or a connection to an external service. The underlying mechanism is simple and efficient: astronomical calculation.

Your Mac (or an app like Solace) uses your latitude and longitude to compute today's exact sunrise and sunset times using the same solar altitude algorithm found in astronomy software. Given a geographic position and a date, the algorithm determines the precise moment the sun crosses the horizon - a calculation that can be performed entirely on-device with negligible CPU cost.

Location only needs to be determined once per session or day. There is no continuous GPS polling. Your Mac knows where it is; the algorithm does the rest. The result is a sunrise and sunset time that updates every 24 hours, shifting by roughly one to four minutes per day depending on the time of year and your latitude.

Both of macOS's built-in solar features use this same approach. Auto appearance (in System Settings > Appearance) triggers the light-to-dark mode switch at calculated sunset time and the dark-to-light switch at sunrise. Night Shift's “Sunset to Sunrise” option similarly shifts colour temperature at the solar events. Neither feature requires you to look up or enter a specific time - the calculation happens invisibly in the background.

Solar Scheduling vs Fixed-Time Scheduling

Both approaches have legitimate use cases. The right choice depends on why you are scheduling your display settings in the first place.

Fixed-time scheduling is consistent and predictable. Your Mac switches at the same clock time every day, regardless of season. This is useful for shift workers, people who work non-standard hours, or anyone whose routine is driven by the clock rather than the sun. The trade-off is that fixed schedules drift out of sync with daylight as the year progresses - sometimes by hours - unless you manually adjust them each season.

Solar-based scheduling is accurate relative to actual daylight. Your Mac switches at the right moment every day without any manual intervention. The switch time changes day by day, which can feel slightly unpredictable at first, but the benefit is that your display settings always match the real light environment outside your window. This is the better choice for anyone whose goal is to align their Mac with natural daylight patterns for sleep, eye comfort, or circadian health.

If you work night shifts or your sleep schedule is deliberately decoupled from the sun, fixed-time scheduling gives you precise, predictable control. For everyone else - anyone who wants their Mac to reflect the natural rhythm of the day - solar scheduling is the superior option.

Which Mac Features Support Solar Scheduling?

Apple has built solar scheduling into two features in macOS, both of which have been available since macOS Mojave.

Auto appearance (System Settings > Appearance > Light/Dark/Auto) switches between light and dark mode at the calculated sunrise and sunset for your location. Select “Auto” and macOS handles the rest. No further configuration is required.

Night Shift “Sunset to Sunrise” (System Settings > Displays > Night Shift) shifts the display's colour temperature towards warmer tones at sunset and returns it to the default white point at sunrise. Like Auto appearance, it uses the same solar algorithm.

Both features require Location Services to be enabled for System Customization. You can check this at System Settings > Privacy & Security > Location Services > System Customization.

There is, however, a significant limitation in the built-in implementation: both Auto appearance and Night Shift are tied to the same sunset trigger. You cannot set dark mode to activate 30 minutes before sunset while Night Shift activates at sunset itself. You cannot shift colour temperature gradually across the afternoon while dark mode switches at a different time. The two settings are coupled to the same single solar event, with no way to configure offsets or independent schedules.

This is where third-party tools become necessary for anyone who wants more granular control. See How to Separate Dark Mode and Night Shift Schedules on Mac for a detailed walkthrough of the options available.

How Solace Implements Solar Scheduling

Solace extends solar scheduling beyond what macOS offers natively, applying it to three separate display dimensions: dark mode, colour temperature, and wallpaper.

Each day, Solace calculates sunrise and sunset for your current location. You can then schedule each setting independently - dark mode does not have to switch at the same moment as colour temperature, and neither has to switch at the same moment as the wallpaper. This makes it possible to build a display schedule that mirrors the gradual transitions of a real day.

Solace also supports optional offsets. If you want dark mode to activate 30 minutes before sunset - to give your eyes time to adjust before the light disappears outside - you can set that offset precisely. You can start warming the colour temperature an hour before sunset and have it reach its warmest point by the time the sun is fully down. These are the kinds of gradual, anticipatory transitions that research on circadian light exposure recommends, and that macOS's binary on/off system cannot replicate.

When you travel across timezones, Solace updates its location automatically. Your solar schedule follows you to Tokyo, New York, or Reykjavik without any manual adjustment. The schedule continues to reflect local sunrise and sunset wherever you are.

Do You Need Location Access for Solar Scheduling?

Yes. There is no way to calculate accurate sunrise and sunset times without knowing where you are. Solar times vary by both latitude and longitude - sunrise in Edinburgh is almost an hour later than sunrise in London on the same day, and sunset differs proportionally. Without a location, the system has no basis for the calculation.

macOS requests location access for solar features under the System Customization category in Location Services. Enabling this allows both Auto appearance and Night Shift's Sunset to Sunrise option to function correctly. Solace requests location access during setup in the same way.

A common concern is privacy. Both macOS and Solace perform all solar calculations entirely on-device. Your location is not sent to any server. The algorithm only needs your latitude and longitude to compute solar times - information that never leaves your Mac. Solace does not store, transmit, or use location data for any purpose other than calculating when the sun rises and sets at your position.

If you prefer not to grant location access, you can use a fixed-time schedule as an alternative. Look up the average sunrise and sunset times for your city at your current time of year, and set those as your fixed schedule. You will need to update them manually every month or so as the seasons change - but it is a viable option for users who want solar-like results without enabling Location Services.

Frequently Asked Questions