The sort function is poorly documented for FM. Too many assumptions are made, like you can figure this out on your own is one of them.
The SORT function by itself is fairly straight forward. Select SORT from the menu, select ascending or descending, and select the field or fields you wish to sort by, in this case your date field.
Try writing a script to do this is the harder, or should say easy part once you know how. A sort script does not allow you to make all of the selections as above. To write the script, select the sort function and close the script. Now manually do a sort exactly as you want the script to behave. The single or multiple fields to search, ascending or descending and perform the sort. Now open up your script and immediately close it. You will be prompted to keep or replace, keep or replace what I use to say. This replace is going to save the last find criteria to your script. Now you can write a script for ascending, another one for descending and so on.
A script can also be written to look at the current status of the sort, and automatically sort in the opposite direction. In other words, click one button to have the field sort ascending, then click the same button again and it knows to sort descending.
Let me know if this helps you.
Marty