Here is the code, that works properly for me:

*--------------
close table all
set century on
create table jdate (_123456789 D)
for ia=1 to 100
insert into jdate values (date()-ia)
endfor
copy to jtest XL5
sele 0
import from jtest.xls xl5
go top
alter table jtest rename column A to _123456789
go top
dele
pack
*-----------------------
Hope this help