Kernel Time and Taskbar Clock

What is it?

This roadmap plans the user-facing side of time: formatted dates and times, a named time-zone table with daylight saving rules, a millisecond uptime, a taskbar clock that opens a calendar flyout, and a Date and time settings page. It was written as if the kernel had no wall clock, but one already ships (see Time and FILETIME), and a basic taskbar clock is already drawn. None of its six sections has shipped; section 1 now has to build on the existing clock rather than add a second one.

How does it work?

Today. Two pieces already exist:

• The kernel clock. The FILETIME wall clock is seeded from UEFI or the CMOS clock at boot and read with KeQuerySystemTime(); user programs reach it through NtQuerySystemTime(). Time zones are a single bias in timezone.h: timezone_set() and filetime_to_local() apply it, but the zone always starts at UTC, there is no daylight saving rule engine, no zone names and no Registry persistence.
• The taskbar clock (partial, section 3). desktop.c draws two lines at the right end of the taskbar: a 12-hour time (3:07 PM) over a YYYY/MM/DD date, in 15 pixel bold, from KeQuerySystemTime() and filetime_to_local(), falling back to the CMOS clock when the wall clock is not ready. The compositor repaints it when the minute changes. It has no click, no flyout, no calendar and no 24-hour option, and the Use24Hour and DateFormat values the Registry already seeds are read by nothing.
• Uptime. uptime() and uptime_ns() exist in timer.h, and the uptime command in cmd.c prints hours, minutes and seconds from the legacy SYS_UPTIME call.

Planned design.

1. Kernel time API: time_now(), time_now_local(), time_to_datetime() and time_set(), which now have to wrap the FILETIME clock rather than keep their own boot anchor.
2. Formatting: strftime-style patterns and the short and long date formats.
3. Taskbar clock: the design's caption-sized clock, checked every second but repainted only when its text changes, with the calendar in the shared 360 pixel flyout.
4. Date and time page: a Settings page to set the time, the zone and the format.
5. Time-zone database: about 30 named zones with daylight saving rules.
6. Monotonic uptime: a millisecond uptime and a days field for the shell command.

flowchart LR
    UEFI[UEFI / CMOS clock] --> WC[FILETIME wall clock]
    NTP[NTP discipline] --> WC
    WC --> TZ[timezone bias]
    TZ --> CLK[taskbar clock]
    TZDB[zone table + DST rules] -.planned.-> TZ
    CLK -.planned.-> CAL[calendar flyout]

What are its interfaces?

How do I use it?

The clock shows in the taskbar after boot (bash scripts/build.sh run), and uptime in the shell prints the time since boot. The kernel clock and time-zone conversion are covered by bash scripts/test.sh SUITE=sched; the taskbar clock has no test.

What is not implemented yet?

• Kernel Time API and Time Formatting.
• Taskbar Clock, which also owns a small defect: without a CMOS clock the fallback path formats a zero-filled date.
• Date/Time Control Panel and Timezone Database.
• Monotonic Uptime Extension.
• Network time sync is planned in NTP, Network Status and Winsock.

How does it compare with Windows 11 and Linux?

Windows 11 reads time with GetSystemTime, converts it with SystemTimeToTzSpecificLocalTime, ships its own zone data with daylight saving rules, and shows a calendar flyout from the taskbar clock. Linux uses clock_gettime(CLOCK_REALTIME) and localtime_r over the IANA zoneinfo files, set with timedatectl. Impossible OS already matches the Windows FILETIME model in the kernel; what this roadmap adds is the zone table, formatting and the clock user interface.

See also

• Kernel Time and Taskbar Clock roadmap
• Time and FILETIME
• Shell design: taskbar and notifications and calendar
• Taskbar