title: Sitemap.xml - should I prefer lastmod to changefreq
body: <p>Since I started use <code>sitemap.xml</code> for my site, I put <code>changefreq: weekly</code> for all significant pages (like algorithms and problems description). This seemed relevant since I sometimes find something to change or fix on these pages and in average each page could be expected to change during a week.</p>
  
  <p>However, the number of pages grew, now I have about 80 of them and though I made changes to some of them, some are surely not changed even in a month.</p>
  
  <p>Meanwhile google-bot scans my pages with almost the same rate, about 15 pages per day (perhaps earlier it was 10 per day) at average. So newly added pages are not scanned as soon as it used to be.</p>
  
  <p>Would it be better to take some efforts and improve my application, so it could generate sitemap with <code>lastmod:YYYY-MM-HH</code> instead? Will it help telling google-bot not to rescan pages which obviously did not change since it scanned them earlier?</p>
  
  <p>I would need to add timestamps to tables involved in rendering pages etc. So I'm curious to know beforehand whether this really should be done.</p>
  
  <p>Thanks in advance!</p>