This is the official manual for the latest Org-mode release.
You can define text snippets with
#+MACRO: name replacement text $1, $2 are arguments
which can be referenced in
paragraphs, verse blocks, table cells and some keywords with
{{{name(arg1,arg2)}}}1. In addition to defined macros,
{{{title}}}, {{{author}}}, etc., will reference
information set by the #+TITLE:, #+AUTHOR:, and similar lines.
Also, {{{date(FORMAT)}}} and
{{{modification-time(FORMAT)}}} refer to current date time
and to the modification time of the file being exported, respectively.
FORMAT should be a format string understood by
format-time-string.
Macro expansion takes place during export.
[1] Since commas separate arguments, commas within arguments have to be escaped with a backslash character. Conversely, backslash characters before a comma, and only them, need to be escaped with another backslash character.