What is the difference between European Community (EC) and European Union (EU) in the regulation reference?

The Lisbon Treaty, the latest primary treaty at EU level, was signed on 13 December 2007 and entered into force on 1 December 2009.
The European Union has been given a single legal personality under this Treaty.
Previously, the European Community and the European Union had different statutes and did not operate the same decision-making rules. The Lisbon Treaty ended this dual system.
On practical terms, all EU legislation has the reference to the EU since 1 December 2009. Up till then, the reference was made to the European Community (EC) as only this body had legal personality.