How to set a value for the input type 'datetime-local'?

Question

I tried this:

\" class=\"date\" name=\"start\" REQUIRED>

H

Answer 1

The answer of Karol Gasienica is a great explanation but somehow did not work for me even in their replies

date('Y-m-d\TH:i:s', $row['Time']); //Gives me 1970-01-01 00:00
date('Y-m-d\TH:i:sP', $row['Time']); //Gives me no display
date("c", strtotime($row['Time'])); //No display too

What worked for me is this

$t = $row['Time'];
date('Y-m-d\TH:i:s', strtotime($t)); // This got it perfectly

However I still voted it up becauce of the explanation.