JSFiddle - React, Tailwind, and code Playground

HTML

<div id="countdown" ></div>
<div id="countdown1" ></div>

JavaScript

fetch("https://cors-anywhere.herokuapp.com/http://worldclockapi.com/api/json/utc/now")
	.then(response => response.json())
	.then(v => new Date(v.currentDateTime))
	.then(processDate);

function processDate(serverDate) {
	const EVENT = {
  	DAY: 5, // Пн - 1, Вт - 2, ..., Сб - 6, Вс - 7
    HOUR: 19,
    MINUTE: 0
  };

	const SECOND = 1000;
	const MINUTE = 60 * SECOND;
	const HOUR = 60 * MINUTE;
	const DAY = 24 * HOUR;
	const WEEK = 7 * DAY;
	const MOSCOW_ZONE = 3 * HOUR;
	const EVENT_TIME = EVENT.DAY * DAY - 4 * DAY + EVENT.HOUR * HOUR + EVENT.MINUTE * MINUTE - MOSCOW_ZONE;

	const clientDate = new Date();
	const now = serverDate.getTime() - clientDate.getTime();
	clockTick();

	function clockTick() {
		const date = new Date(Date.now() + now);
		const eventDate = new Date(Math.ceil((date.getTime() - EVENT_TIME) / WEEK) * WEEK + EVENT_TIME);
		const dt = eventDate - date;
    
    if(dt > WEEK && dt < WEEK - SECOND) {
        // по пятницам в 19:00:00, т. е. в первую секунду игры
        location.reload();
    }
    
    if(dt > WEEK - 45 * MINUTE && dt < WEEK - 45 * MINUTE - SECOND) {
        // по пятницам в 19:45:00, т. е. на 45-ой минуте игры
    }
    
    if(dt > WEEK - 49 * MINUTE && dt < WEEK - 49 * MINUTE - SECOND) {
        // по пятницам в 19:49:00, т. е. на 49-ой минуте игры
    }
   
    
    if(dt > WEEK - 50 * MINUTE) {
			document.getElementById("countdown").innerHTML =
				"Добро пожаловать!!!";
		} else if(dt > WEEK - 6 * HOUR) {
			document.getElementById("countdown").innerHTML =
				"Следующий синхрон через неделю.";
		} else {
			var days = Math.floor(dt / DAY);
			var hours = Math.floor(dt / DAY);

			var hours = toPaddedString(Math.floor((dt % DAY) / HOUR));
			var minutes = toPaddedString(Math.floor((dt % HOUR) / MINUTE));
			var seconds = toPaddedString(Math.floor((dt % MINUTE) / SECOND));

			document.getElementById("countdown1").innerHTML =
				`До начала синхрона осталось: ${days} дн....