To reset Day One Mac 2.0’s password, do the following:
- Open Keychain Access.
- Search for Day One App Locking Password.
- Control click Day One App Locking Password to reveal a contextual menu.
- Select Delete “Day One App Locking Password”.
- Return to Day One to open it without your previously-set password.
Keychain Access can be found by searching Spotlight or going to Finder > Applications > Utilities > Keychain Access.