(I'm assuming that you are using a parameter to query the user about which month they want to print) You can format dates using the CStr() function. For example, if your parameter was called DateToPrint, then the code would be:

CStr({?DateToPrint}, "MM/yy");

On a side note, if you have the option Save Data With Report turned on, then the DataDate and DataTime funtions tell you when the report data was last refreshed.

I have all the date/time functions fully documented in Chapter 6 of my book Crystal Reports Encyclopedia. Since you're new to Crystal Reports, getting a copy will most likely make it much easier for you to learn Crystal Reports.

How are you telling the report to print the 11/07 data?  Are you hard-coding it into the Select Criteria?  If so, the simplest solution is to hard-code the date in the header.

If you have a moving window (e.g., "within the last 30 days" or "last full quarter"), then there are a couple ways to do it.

The simplest, I've found, is to use Minimum({MyReport.MyDate}).  This will return the first date found in the report.  Usually, this is what you are looking for, especially as you are "rounding" it to the month level.  However, occasionally, this can produce odd results.  For instance, if you happen to have 10/31/2007 included, because it was actually a four-week period instead of a true month, this would return "10/07" even if most of the data is "11/07".  Also, if you are doing it by day, and you happen to not have any data for the first day, it goes by the first day you have data, not necessarily the first day in your selected range.

A better option is to simply reproduce your logic in another formula, and use that to generate a date.  Generally, you would put together your formula to look something like:
{MyReport.ReportDate} IN DateAdd("d",-90,CurrentDate) TO DateAdd("d",-60,CurrentDate)

Then, your field in your header might look something like:
CStr(DateAdd("d",-90,DataDate),"MM/yy")