Hi Tuan,

Just go to your Custom CSS > Responsive (tab) > and then you can edit the font-size on this area:

(view large version)

Hi Tuan,

That is coming from the Custom CSS that we added to make Blog page on the Photography demo more special.

Please find this div on your Custom CSS 

.single-blog-holder .blog-content-holder .post-date-and-category .details>div

and remove

padding: 0px; 

from it.

Then add this CSS

.single-blog-holder .details .date {
    padding-left: 0px;
}