What date is used in sorting of FTSearch?

In the Notes help, using FTSearch on the NotesDatabase class tells us we can use the following options:

FT_DATE_ASC (64) sorts by document date in ascending order.

FT_DATE_DES (32) sorts by document date in descending order.

FT_DATECREATED_ASC (1543) sorts by document creation date in ascending order.

FT_DATECREATED_DES (1542) sorts by document creation date in descending order.

FT_SCORES (8) sorts by relevance score (default).

What date does it mean for the FT_DATE_ASC or FT_DATE_DES options? I assume the modified date since there is an option already for creation date.

Please let me know. If it’s modified date, it’s not working for me…

TIA!

Debbie