Joined: 06 Jun 2008 Posts: 8214 Location: Dubuque, Iowa, USA
Have you read the manual (link at the top of the page) on the INTEGER-OF-DATE function? The manual specifically states that INTEGER-OF-DATE converts a YYYYMMDD value into an integer in the range 1 to 3,067,671 (January 1, 1601 to December 31, 9999). Adding 1 to an integer as long as it stays in this range will be fine.
Converting the integer back into a date via the DATE-OF-INTEGER function is listed as being valid for all integers between 1 and 3,067,671. So as long as your integer stays in this range, you can manipulate the value any way you want, being confident that the date resulting will be the correct and valid date.