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function timeAgo(dateInput) {

    const templates = {
        prefix: "",
        suffix: " ago",
        seconds: "less than a minute",
        minute: "about a minute",
        minutes: "%d minutes",
        hour: "about an hour",
        hours: "about %d hours",
        day: "a day",
        days: "%d days",
        month: "about a month",
        months: "%d months",
        year: "about a year",
        years: "%d years"
    };

    let template = (t, n) => templates[t] && templates[t].replace(/%d/i, Math.abs(Math.round(n)));

    let timer = (time) => {
        if (!time) return;
        time = time.replace(/\.\d+/, ""); // remove milliseconds
        time = time.replace(/-/, "/").replace(/-/, "/");
        time = time.replace(/T/, " ").replace(/Z/, " UTC");
        time = time.replace(/([\+\-]\d\d)\:?(\d\d)/, " $1$2"); // -04:00 -> -0400
        time = new Date(time * 1000 || time);

        let now = new Date();
        let seconds = ((now.getTime() - time) * .001) >> 0;
        let minutes = seconds / 60;
        let hours = minutes / 60;
        let days = hours / 24;
        let years = days / 365;

        return templates.prefix + (
			seconds < 45 && template('seconds', seconds) ||
			seconds < 90 && template('minute', 1) ||
			minutes < 45 && template('minutes', minutes) ||
			minutes < 90 && template('hour', 1) ||
			hours < 24 && template('hours', hours) ||
			hours < 42 && template('day', 1) ||
			days < 30 && template('days', days) ||
			days < 45 && template('month', 1) ||
			days < 365 && template('months', days / 30) ||
			years < 1.5 && template('year', 1) ||
			template('years', years)
        ) + templates.suffix;
    };

    return timer(dateInput);
}