For most of my uses I'm not worried about the date/time surviving a board reset as each of my current and foreseen boards is either Ethernet or WiFi based. I will get the current time, via NTP, in setup() every time the board is reset.
The date and time of the file creation, and modification, are not primordial for me. I just wanted to know where and how to be able to control that for future operations and, most importantly, if it is possible. The date and time recordings I need will be in fields inside my files, mostly CSVs, and that's not a problem as I control that inside the files. But when transferring those files from the SD card to my computers I would prefer it is the last modification date and time were correct.
My next project, as soon as I get some more time, is to start working on moving my SD routines from the SD library to the SdFat library as I already need that to correctly return the amount of space available on the SD card. At that time I'll look in to how to possibly set both the file creation date/time and the file modification date/time ... if it's possible.
Thanks all.