気になったらいつでも判定できるようにブックマークレットにした。
javascript:(
function(){
let basis = new Date(2020, 9, 31, 15, 0, 0);
let now = new Date();
let elapsed = now - basis;
let range = 48 * 60 * 60 * 1000;
let quotient = elapsed / range;
let digit = Math.floor(quotient) % 2;
let result = '1 on 1';
if (!digit) {
result = '大乱闘';
}
let remainder = elapsed % range;
let until = new Date(now.getTime() + range - remainder);
let day = ['Sun.', 'Mon.', 'Tue.', 'Wed.', 'Thu.', 'Fri.', 'Sat.'];
result += ` until: ${until.getMonth() + 1}/${until.getDate()} (${day[until.getDay()]}) ${until.getHours()}:${('0'+until.getMinutes()).slice(-2)}`;
alert(result);
}
)();