Where your data lives
In a database on your phone. Without an account, that is the only place it is.
Saving Diary keeps what you log in a database on the device you logged it on. There is no bank connection, nothing is imported from anywhere, and without an account nothing you log leaves the phone.
What changes if you make an account
An account is what puts a copy on the server so a second device can stay in step. That is the trade, and it is worth stating plainly rather than as a feature you switch on: with an account, a copy of your records exists off the phone.
- No account: your records are on this phone and nowhere else
- With an account: a copy is kept so your devices can agree
- Either way there is no bank login, and your records are not sold or used for advertising
The privacy policy is the long version of this answer, and it is linked at the foot of every page.
* Rolling out with an upcoming app update.