davidcalhoun / gps-time.js

Small utility to convert times between GPS epoch (midnight January 6, 1980) and Unix epoch (midnight January 1, 1970), taking into account leap seconds.

gps-time.js

Small utility to convert times between GPS epoch (midnight January 6, 1980) and Unix epoch (midnight January 1, 1970), taking into account leap seconds.

It's not such a trivial matter as adding a constant number of leap seconds to all time inputs! For any two times, a different number of leap seconds may have elapsed between them. This utility helps figure out exactly how many have elapsed.

No dependencies! Very small: 464 bytes gzipped.

Works on the client and on the server (in Node.js).

Node.js installation

npm i --save gps-time

Usage

AMD and CommonJS are supported, with a fallback that defines this utility at window.gpsTime

In Node, you can bring in this utility with this:

var gpsTime = require('gps-time');

Converting from Unix time to GPS time.

var unixMS = Date.now();  // 1454168480000
gpsTime.toGPSMS(unixMS);  // 1138203697000

Converting from GPS time to Unix time.

var gpsMS = 1138203697000;
gpsTime.toUnixMS(gpsMS);  // 1454168480000

Tests

This comes with a small test suite which can be run like this:

$ npm install --dev
$ npm test

License

Licenced under MIT

gps-time.js's Issues

Add typescript typings

Add the typings like described here

declare module 'gps-time' {
    export function toGPSMS(unixMS: number): number;

    export function toUnixMS(gpsMS: number): number;
}

to support typescript usage.

Add function to set GPS leap array

Allow user to manually pass in GPS leap array

Requires rewrite: negative leap second coming?

Negative leap second coming? https://www.telegraph.co.uk/news/2021/01/04/earth-spinning-faster-now-time-past-half-century/

This will require different logic for subtracting rather than adding seconds.

May be a good time to rewrite the library with ESM modules in mind instead of the UMD wrapper.