vhdl-date-format

vhdl-date-format is a variable defined in `vhdl-mode.el'.
Its value is

"%Y-%m-%d"

Documentation:
Specifies the date format to use in the header.
This string is passed as argument to the command `format-time-string'.
For more information on format strings, see the documentation for the
`format-time-string' command (C-h f `format-time-string').

You can customize this variable.