Updating List Item for recalculate the Calculated Columns

Scenario:
You are using calculated columns in your list and you have reference to Today.

Solution:
Run a nightly job

Code:

using Microsoft.SharePoint;
using System.Configuration;

namespace UpdateSPList
{
     class Program
     {
          static void Main(string[] args)
          {
               using(SPSite site = new SPSite(ConfigurationManager.AppSettings["Site"])) {
               using(SPWeb web = site.OpenWeb()) {
               
               SPList list = web.Lists[ConfigurationManager.AppSettings["List"]];
               web.AllowUnsafeUpdates = true;
               foreach (SPListItem item in list.Items)
               {
                   item.SystemUpdate();
               }
               web.AllowUnsafeUpdates = false;
             }
            }
          }
     }
}

Application Configuration File:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="Site" value="http://My_Portal/Sites/TheSite"/>
    <add key="List" value="Tasks"/>
  </appSettings>
</configuration>

Article: