Assign another SAS numeric variable and convert the character-format date string into another SAS variable using the INPUT function with the appropriate INFORMAT. Another option is to generate a SAS macro variable with a discrete list of values using PROC SQL.
that's exactly how I solved it in the meantime. Another solution is to just change the graph. I though about doing a proc gchart where I can define midpoints. As they are quarters that's easy, because they don't need too much space.
The axis statement that I posted earlier (sorry that it was so terse) pre-supposes that the dates will be SAS date values (i.e. days since 01Jan1960).
To force quarters to be the first day of the quarter, I often use the intnx function as follows:
QtrDate=intnx("Quarter',ActualDateValue,0,'b'); This results in values like 01JanYY, 01AprYY,01JulYY,01OctYY when formatted as date5. This date field will then plot very nicely with a qtr increment in the axis statement.