Dates are fruit and so the sugar they contain is essentially fructose, our common "enemy no. 1" :-) The only suitable substitute for sucrose (cane sugar) is glucose. In cooking etc just use twice the amount of "sugar" you would normally use and you should be OK. You can usually buy it in the "home brew" section of the supermarket, but make sure there are no additives in it as they also make "brewers' sugar" which does have some.
JohnN