Formats dates: Just now | 20s | 5m | 10h | 5d | 11 May | 18 Sep, 2017

ago.js

const MONTHS = [
    'Jan',
    'Feb',
    'Mar',
    'Apr',
    'May',
    'Jun',
    'Jul',
    'Aug',
    'Sep',
    'Oct',
    'Nov',
    'Dec'
]

const SECONDS = {
    MINUTE: 60,
    HOUR: 3600,
    DAY: 86400,
    MONTH: 2592000,
    YEAR: 31536000
}

/**
 * @param {Date} date
 * @returns {string}
 */
function formatDay(date) {
    // @ts-ignore
    return String(date.getDate()).padStart(2, '0')
}

/**
 * @param {string|Date} x
 * @returns {string}
 */
export default function ago(x) {
    const date = x instanceof Date ? x : new Date(x)
    // @ts-ignore
    const secondsAgo = Math.floor((new Date() - date) / 1000)

    let interval = Math.floor(secondsAgo / SECONDS.YEAR)
    if (interval >= 1) return `${formatDay(date)} ${MONTHS[date.getMonth()]}, ${date.getFullYear()}`

    interval = Math.floor(secondsAgo / SECONDS.MONTH)
    if (interval >= 1) return `${formatDay(date)} ${MONTHS[date.getMonth()]}`

    interval = Math.floor(secondsAgo / SECONDS.DAY)
    if (interval == 1) return 'Yesterday'
    if (interval > 1) return interval + 'd'

    interval = Math.floor(secondsAgo / SECONDS.HOUR)
    if (interval >= 1) return interval + 'h'

    interval = Math.floor(secondsAgo / SECONDS.MINUTE)
    if (interval >= 1) return interval + 'm'

    return secondsAgo == 0 ? 'Just now' : secondsAgo + 's'
}