formula used for years to format date dont work anymore

Hi,

we are using excel to keep track of the evolution of projects with our customers, in Excel. we used for few years now some vlookup formula to change our text for french or English, depending on the langage spoke by our customers.

for years now, those code was used to format date and works well.

french canadian : [$-C0C]j mmm aaaa;@

English canadian : [$-1009]mmmm j, aaaa;@

now, we have to use those code

french canadian : [$-F800]mmmm j, aaaa

English canadian : [$-1009]mmmm j, aaaa;@ (used for Windows 8)

English canadian : [$-1009]mmmm d, yyyy;@ (used for Windows 7)

but from now on, if users dont modify those information, depending on what platforme they work, the formula dont work.

can someone help me finding out why this change?

thanks!