Last Modified, Dates and Timezones in Sitemapper

Sitemap generator will during its crawl extract last modified values from meta tags and HTTP headers.

Sitemap Generator Last Modified Values

Our software product A1 Sitemap Generator extracts these values in one of the following ways:
  1. Checks if the webserver responds with last-modified HTTP response header:

    HTML pages: The webserver will usually generate this header for you.

    PHP example: Extract last-modified from file:
    <?php header("Last-Modified: " . gmdate("D, d M Y H:i:s", filemtime($SCRIPT_FILENAME)) . " GMT"); ?>.

    ASP example: Set hard coded last-modified:
    <% Response.AddHeader "Last-modified","Mon, 01 Jan 2000 11:22:33 GMT" %>.

    ASP.Net functions you can check documentation on:
    Response.Cache.SetLastModified(DateTime date);
    Response.AddFileDependancy(string filename);
  2. If no relevant HTTP response header, the page is checked for last-modified HTML meta tag.

Understand Timezone and Timestamps

You can always view the last-modified values retrieved in page data.

last modified timestamp for URL

Note: The server timezone will often be placed and configured to be different from your timezone. The date and time the server returns in last-modified depends on the server computer clock. This again depends on how the server timezone and clock has been configured.

Remove LastMod Information in XML Sitemaps

  • Navigate to: Create sitemap | XML sitemap options | Override calculated values.
  • Enable Override LastMod with chosen date/time option.
  • Click Reset button until date shown is 1899.
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