.Net&#x27;s is pretty good.<p><pre><code>    var date = DateTime.UtcNow.AddDays(24).AddYears(-10);
</code></pre>
In use:<p><pre><code>   var billFor = 12; &#x2F;&#x2F; months

   var firstDayOfMonth = DateTime.Today
       .AddDays(1 - DateTime.Today.Day);
    
   var billDates = Enumerable.Range(billFor)
       .Select(n =&gt; firstDayOfMonth.AddMonths(n));</code></pre>