org-agenda-time-leading-zero

org-agenda-time-leading-zero is a variable defined in `org-agenda.el'.
Its value is

nil

Documentation:
Non-nil means use leading zero for military times in agenda.
For example, 9:30am would become 09:30 rather than 9:30.

You can customize this variable.

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