LoginLast Week on My Mac: Seconds out
In 1657, one of the great scientists of the Dutch Golden Age, Christian Huygens, invented the pendulum clock, the first timekeeping device accurate enough to make a second hand worthwhile, as it typically only lost about 15 seconds per day. It was another century before John Harrison developed his marine chronometer, a clock sufficiently accurate to enable precise determinations of longitude. Another hundred years later, with the coming of railways across Europe, ordinary people started synchronising clocks so they caught their train, and our ancestors soon became the first slaves to time.
I’m beginning to wonder whether Apple intends reversing that history. Have you not noticed something odd about setting times in more recent Mac apps, how few allow you to set the seconds? You can see what has happened over the last few years in my log browsers, Ulbow and LogUI.
Most of Ulbow’s interface was written using AppKit seven years ago, and it uses a standard Date Picker with elements containing the year, month, day, hour, minute and second. Given that you can get more than 10,000 log entries in a second, I would have preferred to offer decimal seconds, but that isn’t possible within the standard AppKit picker.
LogUI was written from the start using Apple’s more recent substitute for AppKit, SwiftUI, eighteen months ago. That doesn’t use the AppKit Date Picker, but has its shiny new DatePicker instead. Components available in macOS are there limited to year, month, day, hour and minute. To be able to include seconds your code must be written for an Apple Watch, as macOS, iOS and iPadOS don’t allow seconds at all. That’s why you have to enter them in a separate TextField, although that could perhaps allow the use of decimal seconds.
When I wanted to obtain higher resolution timestamps for log entries in LogUI, I discovered that standard date formatting in macOS only resolves to milliseconds (10^-3 second), and couldn’t stretch to microseconds (10^-6 second), let alone the nanoseconds (10^-9 second) that can be obtained from Mach absolute time, as used internally in parts of macOS. Even that reference has recently become lower resolution, as each ‘tick’ in Apple silicon Macs occurs every 41.67 nanoseconds, rather than once every nanosecond as in Intel Macs.
There’s another difference between Ulbow and LogUI with regard to timestamps that you’re less likely to be aware of: Ulbow obtains its log records indirectly using the log show command, which can include the Mach absolute time of each entry. Instead, LogUI accesses those entries direct through the more recent OSLog API, which doesn’t currently expose such precise times.
Lest this appear too far removed from the world of the user, look in the menu bar clock’s settings, and you’ll see Display the time with seconds is an option, but not the default. When the clock is shown on the Lock Screen or screensaver, it only displays hours and minutes, never seconds, neither can any of the digital clock widgets supplied with macOS. While the Clock app does support decimal seconds, that’s only permitted in its Stopwatch where hundredths are displayed, as they are on an Apple Watch and other devices.
This becomes stranger still when you consider the methods used to synchronise internal clocks. Since High Sierra, macOS has used its own timed service, which Apple describes as “synchronizing the clock with reference clocks via technologies like NTP”, that’s the Internet service provided by time.apple.com as in Date & Time settings. When accessed over the Internet, it’s generally accepted that NTP should be accurate to within tens of milliseconds, although that can at times worsen to 100 milliseconds or more.
As far as I’m aware, no Mac has ever had a GPS receiver built into it, but every iPhone apart from the earliest, and those iPads with cellular support, include assisted GPS and GLONASS. Those are capable of providing time accurate to about 100 and 200 nanoseconds respectively. Even my 11-year-old car corrects its clock using GPS.
Although our Macs and devices can share almost everything else now, my Macs appear unable to adjust their clocks to the more accurate time that should be available to my iPhone. But as iOS is so shy about displaying seconds anywhere, it makes me wonder whether iPhones make full use of GPS time, or mostly rely on that obtained from the nearest cellular mast.
I’m curious whether this is a deliberate campaign to abolish seconds wherever possible, or just the result of doing what looks sufficient. Maybe I’m a mere slave to time, and the Time Lords in Apple Park are on a mission to cure me by travelling back four centuries.
