doesitarm/helpers/parse-github-date.js

// in miliseconds
const units = {
    year  : 24 * 60 * 60 * 1000 * 365,
    month : 24 * 60 * 60 * 1000 * 365/12,
    day   : 24 * 60 * 60 * 1000,
    hour  : 60 * 60 * 1000,
    minute: 60 * 1000,
    second: 1000
}

const rtf = new Intl.RelativeTimeFormat('en', { numeric: 'auto' })

const getRelativeTime = function (d1, d2 = new Date()) {
    var elapsed = d1 - d2

    // "Math.abs" accounts for both "past" & "future" scenarios
    for (var u in units)
        if (Math.abs(elapsed) > units[u] || u == 'second')
            return rtf.format(Math.round(elapsed/units[u]), u)

}

export default function (rawDate) {

    const date = new Date(rawDate)

    return {
        date,
        raw: rawDate,
        timestamp: date.getTime(),
        relative: getRelativeTime(date)
    }
}