It is possible to sign in to Day One Sync with Apple ID. This is to help users sign in without having to remember yet another login.
Day One Android does not support signing in with Apple ID. Also, if you have multiple devices with different Apple IDs, you can use these steps to add an email address to your existing account with Apple ID.
- Go to http://dayone.me/user/login
- Click the link to Authenticate with Apple ID (see screen shot below)
- Log in with your Apple ID.
- Click Account at the top
- Add/update email address - follow on-screen prompts
- You will receive an email to confirm this. Click the link to confirm and sign in to dayone.me with your Apple ID (Authenticate with Apple ID).
- Click Account > Add/change password
Now you can use that email and password to sign in with you choose "Day One account" to sign in on the apps.