relative-time.js

// in milliseconds
var 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-GB', {
    numeric: 'always',
});

/**
 * Returns a human-readable relative time string between two dates.
 *
 * @param {Date|number} d1 - The target date or timestamp to compare.
 * @param {Date|number} [d2=new Date()] - The reference date or timestamp (defaults to now).
 * @returns {string} A formatted relative time string (e.g., "3 days ago", "in 2 hours").
 */
export const getRelativeTime = (d1, d2 = new Date()) => {
    var elapsed = d1 - d2;

    for (var unit in units) {
        if (Math.abs(elapsed) > units[unit] || unit == "second") {
            return rtf.format(Math.round(elapsed / units[unit]), unit)
        }
    }
}