TLDR; After I update my org-mode version, org-time-today function has just disappeared. As awesome coder, I did search in the old versions of org-mode and copied this function from this file to my init! Now everything is perfect!!!
(defun org-time-today ()
"Time in seconds today at 0:00.
Returns the float number of seconds since the beginning of the
epoch to the beginning of today (00:00)."
(float-time (apply 'encode-time
(append '(0 0 0) (nthcdr 3 (decode-time))))))
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