numerically or literally. All these strings specify the same calendar date:
@example
-1970-9-17 # ISO 8601.
+1970-09-17 # ISO 8601.
70-9-17 # This century assumed by default.
70-09-17 # Leading zeros are ignored.
9/17/72 # Common U.S. writing.
@cindex date format, ISO 8601
For numeric months, the ISO 8601 format
@samp{@var{year}-@var{month}-@var{day}} is allowed, where @var{year} is
-any positive number, @var{month} is a number between 1 and 12, and
-@var{day} is a number between 1 and 31. If @var{year} is less than 100,
-then 1900 is added to it to force a date in this century. The construct
+any positive number, @var{month} is a number between 01 and 12, and
+@var{day} is a number between 01 and 31. A leading zero must be present
+if a number is less than ten. If @var{year} is less than 100, then 1900
+is added to it to force a date in this century. The construct
@samp{@var{month}/@var{day}/@var{year}}, popular in the United States,
is accepted. Also @samp{@var{month}/@var{day}}, omitting the year.