org-read-date-force-compatible-dates

org-read-date-force-compatible-dates is a variable defined in `org.el'.
Its value is

t

Documentation:
Should date/time prompt force dates that are guaranteed to work in Emacs?

Depending on the system Emacs is running on, certain dates cannot
be represented with the type used internally to represent time.
Dates between 1970-1-1 and 2038-1-1 can always be represented
correctly. Some systems allow for earlier dates, some for later,
some for both. One way to find out it to insert any date into an
Org buffer, putting the cursor on the year and hitting S-up and
S-down to test the range.

When this variable is set to t, the date/time prompt will not let
you specify dates outside the 1970-2037 range, so it is certain that
these dates will work in whatever version of Emacs you are
running, and also that you can move a file from one Emacs implementation
to another. WHenever Org is forcing the year for you, it will display
a message and beep.

When this variable is nil, Org will check if the date is
representable in the specific Emacs implementation you are using.
If not, it will force a year, usually the current year, and beep
to remind you. Currently this setting is not recommended because
the likelihood that you will open your Org files in an Emacs that
has limited date range is not negligible.

A workaround for this problem is to use diary sexp dates for time
stamps outside of this range.

You can customize this variable.

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