JSFiddle - React, Tailwind, and code Playground

by SĂ©bastien Lorentz

JavaScript

const startTime = '03:05+0830';

// 2019-03-31 3:15 => GMT+0200
// 2019-03-30 22:05 GMT+0100

const [, newStartTime] = (/(\d{2}:\d{2}):\d{2} GMT([+-]\d{4})?/g).exec(new Date(`${new Date().toISOString().substring(0,10)}T${startTime}`).toTimeString());

console.log(newStartTime);