org-agenda-sorting-strategy: items containing no time-of-day specification first

Question

The manual says

For the daily/weekly agenda, the items for each day are sorted. The default order is to first collect all items containing an explicit time-of-day specification.

    8:30-13:00 Arthur Dent lies in front of the bulldozer
    12:45...... Ford Prefect arrives and takes Arthur to the pub
    14:00-15:00 TODO Call John regarding memo
    19:00...... The Vogon reads his poem
    20:30-22:15 Marvin escorts the Hitchhikers to the bridge
    TODO send newsletter to mailing list
    TODO buy John birthday gift           :errands:
    Internship period for Alex

How can I tweak `org-agenda-sorting-strategy' so that I can first display all items containing no time-of-day specification like in

    Internship period for Alex
    TODO send newsletter to mailing list
    TODO buy John birthday gift           :errands:
    8:30-13:00 Arthur Dent lies in front of the bulldozer
    12:45...... Ford Prefect arrives and takes Arthur to the pub
    14:00-15:00 TODO Call John regarding memo
    19:00...... The Vogon reads his poem
    20:30-22:15 Marvin escorts the Hitchhikers to the bridge

Answer 1

You have to set org-sort-agenda-notime-is-late to nil. It is defined in org-agenda.el and, by default, the value is t (see also it's use in org-cmp-time).

Non-nil means items without time are considered late. This is only relevant for sorting. When t, items which have no explicit time like 15:30 will be considered as 99:01, i.e. later than any items which do have a time. When nil, the default time is before 0:00. You can use this option to decide if the schedule for today should come before or after timeless agenda entries.

Answer 2

Check the current setting of org-agenda-sorting-strategy. It should be something like this:

((agenda time-up priority-down category-keep)
 (todo priority-down category-keep)
 (tags priority-down category-keep)
 (search category-keep))

Changing the order of sorting strategies for the agenda should do what you want:

(setq org-agenda-sorting-strategy 
    '((agenda priority-down category-keep time-up)
      (todo priority-down category-keep)
      (tags priority-down category-keep)
      (search category-keep)))

Read the documentation of the variable for more information.

EDIT: As the OP points out in the comments, this does not work. It should be possible to do what he wants using a user-defined comparison function as described in my comment below, but that is TBD.