How can add the date and time to the sitemap?

Currently we are using an auto generator sitemap, but this sitemap does not show the date & time, then how can added a date & time?

Here is my site Read-Only: LINK
(how to share your site Read-Only link)

By using a custom sitemap. A manual process that you would need to maintain when adding new items.

It looks like this on my website:
That is, you need to add a lastmod tag with a date in the code of sitemap

Yes, I know to add the custom code but this process is a manual process, I am going to every time manually change the sitemap, can you suggest any other solution provide some like Third party integration? so when I update the website that time auto change the custom sitemap.

Interested to know this

But, how can add in my website??