How to put date after the “Written by” area?

Unfortunately, your site does not load, so I can’t see if the date is there and hidden (and might be revealed via CSS) or not output. If the latter, then this is a theme issue and is best addressed with the authors of your theme.

My site is loading here.

The author of the theme never replied my questions.

The theme’s not outputting a date. You’re using a commercial/premium theme, so please use their official support channel. We feel they are best equipped to support their products.

https://themehybrid.com/

Commercial products are not supported in these forums.

I’m not using a commercial theme, I downloaded it for free years ago. There is no necessity to answear a question if you can’t help.

Unfortunately, that theme is not supported here. If there are no longer any updates happening, you could edit it. Find the file that outputs that author line and add a date using https://developer.www.ads-software.com/reference/functions/get_the_date/ or https://www.wpbeginner.com/wp-tutorials/display-the-last-updated-date-of-your-posts-in-wordpress/