The thing is, if the date reported by smbios tables is 05/02/2015 (which is bigger than 04/01/2014) so: If smbios tables are in fseg - Windows will select the most recent date - 05/02/2015 If not - Windows will select the most recent date (the only one it found) - 04/01/2014
So 'char win_bios_date VARFSEG = " 04/01/2014 “‘ will not help.
Why would the smbios tables have a newer date? If you mean that qemu is providing smbios table 0 and its date is newer,
qemu doesn't provide table 0 (by default, possibly there is a obscure command line switch to change that), so seabios will generate it and the two dates should match.
I kind of fail to see the problem the patch series tries to solve ...