Swatch Time: Sample Code

This repository contains single-file examples that compute Swatch Internet Time ("beats") using the canonical definition used by the SwatchTime organization.

Canonical rules

• Reference zone: Biel Mean Time (BMT) = UTC+1 (fixed offset, no DST)
• One beat = 86.4 seconds (86400 / 1000)
• Beats run from @000 at Biel midnight (00:00:00 UTC+1) through @999 just before the next Biel midnight

Computation (pseudocode)

// JavaScript-style pseudocode
now = new Date()
utcSeconds = now.getUTCHours() * 3600 + now.getUTCMinutes() * 60 + now.getUTCSeconds()
bielSeconds = (utcSeconds + 3600 + 24*3600) % (24*3600)
beat = Math.floor(bielSeconds / 86.4) % 1000
display = `@${String(beat).padStart(3,'0')}`

Quick test vectors

• 2025-01-01T00:00:00Z → Biel 01:00:00 → @041
• 2025-01-01T23:00:00Z → Biel 00:00:00 (next day) → @000
• 2025-06-01T12:34:56Z → Biel 13:34:56 → @565

Files

• bash/get_swatch_time.sh — Bash example. Run with bash bash/get_swatch_time.sh.
• c/get_swatch_time.c — C single-file example. Build: gcc -std=c11 c/get_swatch_time.c -o get_swatch_time -lm.
• cpp/get_swatch_time.cpp — C++ single-file example. Build: g++ -std=c++11 cpp/get_swatch_time.cpp -o get_swatch_time.
• csharp/get_swatch_time.cs — C# example. Run with dotnet script or compile as a console app.
• elixir/get_swatch_time.exs — Elixir example. Run with elixir elixir/get_swatch_time.exs.
• go/get_swatch_time.go — Go single-file example. Build or run with go run go/get_swatch_time.go.
• haskell/get_swatch_time.hs — Haskell example. Run with runhaskell haskell/get_swatch_time.hs or compile with ghc.
• java/GetSwatchTime.java — Java example. Build/run with javac java/GetSwatchTime.java && java -cp java GetSwatchTime.
• js/getSwatchTime.js — JavaScript single-file example. Run with node js/getSwatchTime.js or open in browser console.
• kotlin/get_swatch_time.kt — Kotlin example. Run as script with kotlinc -script kotlin/get_swatch_time.kt or compile with kotlinc.
• lua/get_swatch_time.lua — Lua example. Run with lua lua/get_swatch_time.lua.
• php/get_swatch_time.php — PHP example. Run with php php/get_swatch_time.php.
• powershell/get_swatch_time.ps1 — Windows PowerShell example. Run in PowerShell: powershell -File powershell/get_swatch_time.ps1.
• python/get_swatch_time.py — Python 3 single-file example. Run with python3 python/get_swatch_time.py.
• ruby/get_swatch_time.rb — Ruby example. Run with ruby ruby/get_swatch_time.rb.
• rust/get_swatch_time.rs — Rust single-file example that uses SystemTime. Compile with rustc rust/get_swatch_time.rs && ./get_swatch_time or run with cargo if you prefer.
• swift/get_swatch_time.swift — Swift example. Run with swift swift/get_swatch_time.swift.

Usage

Each file prints the current Swatch beat to stdout/console. Some files accept an ISO timestamp or include example test lines you can uncomment to test known vectors.

Note: Rounding and display (important)

When displaying centibeats (two decimal places), implementations that round the fractional beats to 2 decimals before wrapping can briefly produce a value of 1000.00 (for example when the raw value is 999.995). To avoid this transient display, round first then wrap values >= 1000 back into range (subtract 1000 or set to 0) before formatting for display.

Canonical JavaScript snippet each implementation should follow:

const rawBeats = bielSeconds / 86.4;
let rounded = Math.round(rawBeats * 100) / 100; // 2 decimals
if (rounded >= 1000) rounded = rounded - 1000;   // wrap 1000 -> 0
const display = rounded.toFixed(2);

This preserves human-friendly rounding while ensuring the UI never shows 1000.00 briefly.

License

MIT