"Calendar agent wants to use the login keychain"

Back up all data.

Launch the Keychain Access application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Keychain Access in the icon grid.

Select the login keychain from the list on the left side of the Keychain Access window. If your default keychain has a different name, select that.

If the lock icon in the top left corner of the window shows that the keychain is locked, click to unlock it. You'll be prompted for the keychain password, which is the same as your login password, unless you've changed it.

Right-click or control-click the login entry in the list. From the menu that pops up, select Change Settings for Keychain "login". In the sheet that opens, uncheck both boxes, if not already unchecked.

From the menu bar, select

Keychain Access ▹ Preferences ▹ First Aid

If the box marked Keep login keychain unlocked is not checked, check it.

Select

Keychain Access ▹ Keychain First Aid

from the menu bar and repair the keychain. Quit Keychain Access.

Do you have two step authentication setup up for the account? if yes, you need to enter a new authentication password instead of the account password.

Other options to repair.

Open Keychain Access in Applications/Utilities and under Keychain in the Menu bar run Keychain First Aid.

Open System Preferences > Internet Accounts. Remove the account then add it back.

The Calendar might need the password information for an account you are subscribed to. It is asking for you permission to allow Calendar to retrieve the password from the keychain.

Perfect! I had this same problem after doing a full restore of my system, and you completely solved it for me. Thank you!

Thanks! Answer from Linc Davis worked well - and better described than a few (similar) solutions elsewhere.

Thank you Linc Davis -- helped me too!

I've had this problem for weeks and never could find the answer, in 5 minutes I was fixed. Thank you so much.

Likewise - this sorted a long-running irritation for me!

Huge help, thanks so much!

Thanks - worked like a charm

I get this 'CalendarAgent wants to use "login" keychain' message when I'm trying to log in to my laptop.

I haven't set up any keychains.

Help?

p.s. I have a mac book pro Yosemite

I have this exact same issue and have completed all the first aid and password changes and other methods in Keychain Access, including deleting most of them. So frustrating!