It is located in wp-includes/general-template.php and
the_weekday_date() only outputs the day if the current post’s weekday is different from the previous one output (why this would be needed, I have no idea).
The filter accepts three arguments:
$the_weekday_dateThe day of the week
$beforeText or markup before
$afterText or markup after
The original value of
$the_weekday_date is determined using a chain of functions to snag the localized day of the week:
get_weekday()method of the
Let’s say you wanted to convert the day ‘Saturday’ into pirate-speak, something like ‘SatARRRday’ and were using
the_weekday_date() to output it in the Loop.