Excel international date formatting - c++

Question

I am having problems formatting Excel datetimes, so that it works internationally. Our program is written in C++ and uses COM to export data from our database to Excel, and this includes datetime fields.
If we don't supply a formatting mask, some installations of Excel displays these dates as Serial numbers (days since 1900.01.01 followed by time as a 24-hour fraction). This is unreadable to a human, so we ha found out that we MUST supply a date formatting mask to be sure that it displays readable.
The problem - as I see it - is that Excel uses international formatting masks. For example; the UK datetime format mask might be "YYYY-MM-DD HH:MM".
But if the format mask is sent to an Excel that is installed in Sweden, it fails since the Swedish version of the Excel uses "ÅÅÅÅ-MM-DD tt:mm".
It's highly impractical to have 150 different national datetime formatting masks in our application to support different countries.
Is there a way to write formatting masks so that they include locale, such that we would be allowed to use ONE single mask?

Answer 1

Unless you are using the date functionality in Excel, the easiest way to handle this is to decide on a format and then create a string yourself in that format and set the cell accordingly.
This comic: http://xkcd.com/1179/ might help you choose a standard to go with. Otherwise, clients that open your file in different countries will have differently formatted data. Just pick a standard and force your data to that standard.
Edited to add: There are libraries that can make this really easy for your as well... http://www.libxl.com/read-write-excel-date-time.html
Edited to add part2: Basically what I'm trying to get at is to avoid asking for the asmk and just format the data yourself (if that makes sense).

Answer 2

I recommend doing the following: Create an excel with date formatting on a specific cell and save this for your program to use.
Now when the program runs it will open this use this excel file to retrieve the local date formatting from the excel and the specified cell.
When you have multiple formats to save just use different cells for them.
It is not a nice way but will work afaik.
Alteratively you could consider creating an xla(m) file that will use vba and a command to feed back the local formatting characters through a function like:
Public Function localChar(charIn As Range) As String
localChar = charIn.NumberFormatLocal
End Function
Also not a very clean method, but it might do the trick for you.