For some reason ADT (Eclipse) won’t pick up on the fact that it does in fact need to be updated. Since the built in tools for updating are failing you you’ll have to work around them. On the Help menu instead of selecting Check for Updates instead pick Install New Software
Step : 1
Help > Install New Software.
Step : 2
On the Available Software screen in the Work With drop down provide:
https://dl-ssl.google.com/android/eclipse/ if it’s not already available.
Step : 3
Check everything that you want to update. In the list of checkboxes below uncheck “Contact all update sites during install to find required software.”
Step : 4
Click Next and follow the remaining onscreen prompts.
Step : 5
You may be warned that instead of an install an update will be performed. This is okay.
Once the operation is complete you will no longer receive the “The Android SDK requires Android Developer Toolkit verxion 21.1.0 or above” error when you load ADT.
Example Screen :
Reference : http://stackoverflow.com/questions/15105730/when-i-load-adt-why-do-i-receive-the-error-the-android-sdk-requires-android-dev/15105731#15105731