doc: Clarify that heuristics are used to detect the format of a date …

…string (bug #64563).

* scripts/time/datevec.m: Add sentences in the documentation to clarify that
heuristics are used when no format string is provided.

scripts/time/datevec.m

@@ -36,12 +36,15 @@
 ## month, day, hour, minute, and seconds respectively.
 ##
 ## @var{f} is the format string used to interpret date strings
-## (@pxref{XREFdatestr,,@code{datestr}}).  If @var{date} is a string, but no
-## format is specified, then a relatively slow search is performed through
-## various formats.  It is always preferable to specify the format string
-## @var{f} if it is known.  Formats which do not specify a particular time
-## component will have the value set to zero.  Formats which do not specify a
-## date will default to January 1st of the current year.
+## (@pxref{XREFdatestr,,@code{datestr}}).  If @var{date} is a string or a cell
+## array of strings, but no format is specified, heuristics are used to guess
+## the input format.  These heuristics could lead to matches that differ from
+## the result a user might expect.  Additionally, this involves a relatively
+## slow search through various formats.  It is always preferable to specify the
+## format string @var{f} if it is known.  Formats which do not specify a
+## particular time component will have the value set to zero.  Formats which do
+## not specify a particular date component will default that component to
+## January 1st of the current year.
 ##
 ## @var{p} is the year at the start of the century to which two-digit years
 ## will be referenced.  If not specified, it defaults to the current year minus