pebble-ifc-complication

A lightweight, reusable International Fixed Calendar (IFC) widget / complication for Pebble watchfaces.

This package provides a simple update() function that returns the current IFC date as a short string, ready to display in a text layer (e.g., "Mar 1 Sun" or "Jun 29 LPD").

Published as a Pebble Package so watchface developers can easily integrate it with:

pebble package install pebble-ifc-complication

Features

• Accurate International Fixed Calendar calculation
• Handles leap years and Year Day / Leap Day correctly
• Option to use UTC time for global sync (date rollover at 00:00 UTC)
• Short, watch-friendly output strings
• No dependencies — pure JavaScript, tiny footprint

International Fixed Calendar Rules (Important – Do Not Change Lightly)

This implementation follows the standard Cotsworth/Eastman IFC rules:

• 13 months × 28 days = 364 days base
• Months: Jan, Feb, Mar, Apr, May, Jun, Sol, Jul, Aug, Sep, Oct, Nov, Dec
• Every month starts on Sunday and ends on Saturday (perpetual calendar)
• Leap Day: Inserted as an extra day after June 28 (in leap years only) — shown as "Jun 29 LPD"
• Year Day: Extra day after December 28 — shown as "Dec 29 YRD"
• Both Leap Day and Year Day have no weekday (they are holidays outside the week)
• Leap year rule: same as Gregorian (div by 4, but not 100 unless 400)
• Day numbering: normal days 1–28 per month; specials are "29" visually for calendar flow

Why 3-character codes for specials (LPD / YRD)?

• Most Pebble watchfaces render complications in very small text areas.
• Weekdays are almost always abbreviated to 3 letters ("Sun", "Mon", "Tue", etc.) to avoid ambiguity (T = Tue or Thu? S = Sat or Sun?).
• Using "LPD" (Leap Day) and "YRD" (Year Day) keeps the same 3-character width and visual rhythm — it looks like a weekday abbreviation but clearly isn't.
• This prevents layout breaks when the complication is placed where a normal weekday would go.
• One-letter ("L"/"Y") or two-letter ("LD"/"YD") options may exist in some watchfaces but are less common and can cause alignment issues.
• Do not change the output format to full words ("Leap Day", "Year Day") without a config option — it will break many faces. If someone wants longer text, they can fork or wrap the output.

Installation

pebble package install pebble-ifc-complication

Usage

const ifc = require('pebble-ifc-complication')

// Basic Usage (local time)
var ifcText = ifc.update();    // e.g. "Mar 1 Sun"

// With UTC for global sync
var ifcTextUTC = ifc.update({ useUTC: true });   // date calculated from UTC

// In a tick handler (example)
watch.addEventListener('minutechange', function(e) {
  textLayer.text = ifc.update({ useUTC: false });
});

Output Examples

| Date (Gregorian) | IFC Output | Notes | | ---------------- | ---------- | -------------------- | | 2026-02-27 | Mar 1 Sun | Normal Day | | 2024-06-28 | Jun 28 Sat | Last day of June | | 2024-06-29 | Jun 29 LPD | Leap Day (leap year) | | 2024-06-30 | Sol 1 Sun | First day of Sol | | 2024-12-31 | Dec 29 YRD | Year Day |

Testing the Package Locally

1. In your package folder: npm link
2. In a test CloudPebble watchface project:

pebble package install pebble-ifc-complication

3. Require and call in your code (as shown above).
4. Build and run in emulator to verify output on real dates (try 2024-06-29 for Leap Day)

Contributing

• Keep output to short strings (3-char weekdays or LPD/YRD)
• Do not alter the core IFC rules (month order, leap insertion, Sunday starts, etc.) as they are standard and intentional.
• Add new config options (e.g., { format: 'long' }) instead of breaking the default.
• PRs welcome for bug fixes, better error handling, or more config flags.

License

MIT