change in frequency help you to fetch data by Google bots or search engine bots.... if frequency is day mean it will fetch daily if any change occur in your site hope you understand.
Oh, we wish Here is what www dot sitemaps dot org ("protocol" section) says about "<changefreq>": Please note that the value of this tag is considered a hint and not a command. Even though search engine crawlers may consider this information when making decisions, they may crawl pages marked "hourly" less frequently than that, and they may crawl pages marked "yearly" more frequently than that. Crawlers may periodically crawl pages marked "never" so that they can handle unexpected changes to those pages.
Hi, Change frequency in a sitemap is all about how frequently the content at a particular URL is likely to change.
It is how often you are saying that page's content is updated. The search engine spiders will read it, but will almost certainly make up their own mind about how often your site is updated based on their crawl results.
As you know very well, Search Engine likes updates at your website. If you are doing updation daily basis then you can mention daily in sitemap or weekly for weekly updation at particular webpage. If your website updation is good and necessary then your updation will be listed or crawled according to your priority and change frequency.