generateTimestamp.html

<script src="moment.min.js"></script>
<script>
  moment().utc();

  calculate = () => {
    document.querySelector('#result').innerText = '';

    const operation = document.querySelector('#operation').value;
    const value = document.querySelector('#value').value;
    const unit = document.querySelector('#unit').value;

    const result = moment()[operation](value, unit);

    document.querySelector('#result').innerText = result.format('X');
  }
</script>
<h1>Generate Timestamp using Solidity Time Units Online</h1>
Current
<select id="operation">
  <option>add</option>
  <option>subtract</option>
</select>
<input type="number" id="value">
<select id="unit">
  <option>seconds</option>
  <option>minutes</option>
  <option>hours</option>
  <option>days</option>
  <option>weeks</option>
  <option>years</option>
</select>
<button onclick="calculate()">Calculate</button>
<pre id="result"></pre>