for audio, CD quality MP3s (128kbps) will take up 1MB per minute (approx, of course) while WMA at equivalent quality (at 64kbps) will take up half of what MP3 need. So, a 256MB card is good for approx 4 hours worth of music (your 256MB card will hold a max of 245MB, illogical, I know).
As for video, read the excellent guide on this forum about encoding video in DivX format. My previous thread on video size might help
http://www.aximsite.com/boards/showt...ght=video+size
As for world clock, you can change the clock on your Ax from "local" to "visiting" and it should do the trick (start - settings - system - clock; then set the clock to wherever you are visiting).