org-agenda-current-time-string

org-agenda-current-time-string is a variable defined in `org-agenda.el'.
Its value is

"now - - - - - - - - - - - - - - - - - - - - - - - - -"

Documentation:
The string for the current time marker in the agenda.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.