I have now looked at the example for a datalogger but maybe I should have told you that I have bought the "Datalogging Arduino Shield" from Adafruit with built-in RTC?
Anyway, I am attaching a cleaned-up version of the example code. The clean-up consist of getting rid of all UART commands which I seem to think is unneccesary when it comes to simple data storing to SD (I just need two columns i.e Data & Time).
The use for UART (I hardly know what I'm talking about but SD communication seem to be over SPI) is simply unneccesary as long as there is no problem with the code (otherwise it would however be nice with some debugging possibillity...).
If i'm not totally misstaken I can use attached code and just try to enable the built-in RTC also (however that is done). The RTC will of course also have to be set once and somehow.
I also think I understand that the data type for logging purposes seem to be "String".
I have printed out the 63 page manual for the above logger shield and I will read it soon.