In the Advanced settings there is a button labeled “Rebuild Index”. This button allows our support team to help customers who are having trouble with searching.
In order to perform fast text searches, Day One maintains a separate database of search terms. Normally this database is kept in sync as changes are made to an entry file. In the rare case it isn’t, this button allows you to rebuild the database from scratch using the current entry text. If you notice entries missing in search results, or Day One crashes when you try to search, rebuilding the index may help.