I see big differences when using the two calls to "org-agenda-time-grid" with identical parameters.
(setq tm '(number-sequence 800 2000 100)) (setq org-agenda-time-grid '((today daily require-timed) 'tm "" "----------------")) (setq org-agenda-time-grid '((today daily require-timed) (800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 2000) "" "----------------")) Regards Steve