How to hide blog date header

That is not difficult to do. Sign into Dashboard > Design > Edit HTML to open the template editor and look for the block of code like the one below (for the Minima template, yours depending on your template may be slightly different):

/* Posts
-----------------------------------------------
*/
h2.date-header {
margin:1.5em 0 .5em;
}


and just add this line: visibility:hidden; for example like below:

/* Posts
-----------------------------------------------
*/
h2.date-header {
visibility:hidden;
margin:1.5em 0 .5em;
}


and the date header will be gone.