You can edit aspects any of your journals in Day One, including the default Journal.
Basic: 1 journal
Plus (legacy): up to 10 journals
Premium: unlimited journals
Go to Settings
Use the sliders on the right of the journal names to rearrange the order of journals. Tap the journal you wish to edit.
After tapping one of the journals, see options to edit the journal name, description, color, and advanced settings. In the Advanced settings, there are several options to tailor the journal. View the Journal ID (used for customer support issues), Encryption status, add a Default Template, show in On This Day, Show in Today View, Include in Streaks. Options to control local storage options for a particular journal can also be set.
Tap the More button (•••) at the top right of the Timeline view, then Journal Settings or tap the Journal name to open Journal settings.
Click Day One in the file menu
Click the Journals tab
Click a journal to highlight
Click the "i" to the right of the journal
Right-click (or Control+click) on any journal in the journal drawer. Then choose Edit Journal
Click the More button (•••) on the entry view pane and choose Edit Journal.
Tap Settings (In the sidebar or three-dots button in the upper-right).
Tap the journal you wish to rename.
Tap the journal name at the top of
Tap the checkmark to save the new name