Sets the last time the bookmark for @uri was last modified.
If no bookmark for @uri is found then it is created.
The "modified" time should only be set when the bookmark's meta-data
was actually changed. Every function of #GBookmarkFile that
modifies a bookmark also changes the modification time, except for
g_bookmark_file_set_visited_date_time().
Sets the last time the bookmark for @uri was last modified.
If no bookmark for @uri is found then it is created.
The "modified" time should only be set when the bookmark's meta-data was actually changed. Every function of #GBookmarkFile that modifies a bookmark also changes the modification time, except for g_bookmark_file_set_visited_date_time().