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Solar Time Daemon

TimeNow provides standalone system daemons that compute solar time offsets without requiring the JVM backend. These are designed for Linux kernel integration, embedded systems, and scientific infrastructure.

Available Implementations

Daemon Language Kernel Compatible Dependencies
timenow-daemon C99 Via userspace libm only
timenow-daemon-rs Rust no_std crate libm (Rust)

Both implementations use the same NOAA solar position algorithms (reference) and produce equivalent results.

Architecture

              ┌──────────────────┐
              │  GPS / Config    │
              │  --lat  --lng    │
              └────────┬─────────┘
                       │
              ┌────────▼─────────┐
              │  timenow-daemon  │
              │  (C99 or Rust)   │
              │                  │
              │  NOAA solar math │
              │  signal handling │
              │  atomic writes   │
              └──┬─────┬─────┬──┘
                 │     │     │
    ┌────────────▼┐ ┌──▼───┐ ┌▼────────────┐
    │/run/timenow/│ │/run/ │ │/dev/shm/    │
    │solar_offset │ │solar │ │timenow      │
    │(plain text) │ │.json │ │(SHM struct) │
    └─────────────┘ └──────┘ └──────┬──────┘
                                    │
                           ┌────────▼────────┐
                           │  chrony / NTP   │
                           │  refclock SHM   │
                           └─────────────────┘

Quick Start

C Daemon

cd daemon && make
./timenow-daemon --lat=48.2 --lng=16.37 --foreground

Rust Daemon

cd daemon-rust && cargo build --release
./target/release/timenow-daemon-rs --lat=48.2 --lng=16.37

CLI Flags

C Daemon

Flag Required Default Description
--lat=DEG Yes — Latitude (-90 to 90)
--lng=DEG Yes — Longitude (-180 to 180)
--interval=SEC No 1 Update interval in seconds
--foreground No off Run in foreground (skip daemonization)
--help No — Show usage

Rust Daemon

Flag Required Default Description
--lat=DEG Yes — Latitude (-90 to 90)
--lng=DEG Yes — Longitude (-180 to 180)
--interval=SEC No 60 Update interval in seconds
--help / -h No — Show usage

Output Files

C Daemon

Path Format Content
/run/timenow/solar_offset Plain text Offset in seconds (e.g. -1054.234567)
/run/timenow/solar.json JSON (pretty) Full solar data
/dev/shm/timenow Key-value offset, clock_sec, clock_nsec, precision, leap
/run/timenow/timenow.pid Plain text Process ID

Rust Daemon

Path Format Content
/run/timenow/solar_offset_rs Plain text Offset in seconds
/run/timenow/solar_rs.json JSON (compact) Full solar data + declination
/dev/shm/timenow_rs Plain text Offset value

Sample JSON (C Daemon)

{
  "timestamp": "2025-01-15T12:30:00Z",
  "latitude": 48.208200,
  "longitude": 16.373800,
  "solar_noon_utc": 11.823456,
  "sunrise_utc": 6.712345,
  "sunset_utc": 16.934567,
  "elevation_deg": 18.4523,
  "azimuth_deg": 192.3401,
  "equation_of_time_min": -9.2345,
  "day_length_hours": 8.4567,
  "solar_offset_sec": -1054.234567
}

Sample JSON (Rust Daemon)

{
  "lat": 48.208200,
  "lng": 16.373800,
  "solar_noon_utc": 11.823456,
  "sunrise_utc": "06:42:44",
  "sunset_utc": "16:56:05",
  "elevation_deg": 18.4523,
  "azimuth_deg": 192.3401,
  "equation_of_time_min": -9.2345,
  "day_length_hours": 8.4567,
  "solar_offset_sec": -1054.234567,
  "declination_deg": -18.1234
}

Implementation Differences

Aspect C Daemon Rust Daemon
Default interval 1 second 60 seconds
Daemonization Double-fork Foreground only
Atomic writes Yes (temp + rename) Direct creation
JSON format Pretty-printed Compact single-line
Sunrise/sunset in JSON Numeric (hours) Formatted HH:MM:SS
Polar handling Horizon angle check NaN for sunrise/sunset
Logging Silent unless --foreground Always logs to stderr

Polar Day/Night

Both daemons handle extreme latitudes where the sun may not rise or set:

  • C daemon: Returns computed horizon angle; sunrise/sunset may be absent.
  • Rust daemon: Returns NaN for sunrise/sunset, sets day length to 24.0 (midnight sun) or 0.0 (polar night). JSON displays "--:--:--" for missing values.