Why I can delete my user from an old phone without deleting everything on my new one? So, I bought a new phone (Nexus 5) and I created my account and user. My old phone (Nexus 4) has the same user as a matter of fact, the problem is that I gave my old phone to my mother so she could have a better phone. But, several things are sync between the phones, like the photos and the calendar. I tried to create a new user for her or even delete my user from the old phone but I couldn't find any option to do that. Any suggestion on how to solve that? 
Thank you in advance!
You need to create a new Google account for your mother, and then delete your own Google account from the phone.

To add an account:


  
  On your mobile device, open the Settings menu .
  Under "Accounts," touch Add account. 
  


This is how to delete your account. 


  If you're using a device with multiple users, each user has separate account settings so make sure you’re logged in as the correct user before removing any account information.
  
  
  Open the Settings menu  on your device.
  Under "Accounts," touch the name of the account you want to remove.
  If you’re using a Google account, touch Google and then the account. Important: When you remove your Google Account, all the email, contacts, Calendar events, and other data associated with that account will no longer automatically sync with your device. 
  Touch the Menu icon Menu in the top right corner of the screen.
  Touch Remove account. If this is the only Google account on the device, you may need to enter your device's pattern, PIN, or password as a security measure. This ensures that only you or someone you trust is removing the account from your device.
  


Source: https://support.google.com/nexus/answer/2840815?hl=en