When did Finland and Sweden join NATO?
Russia's invasion of Ukraine prompted Finland and Sweden to apply for NATO membership in May 2022, and the ratification process for Sweden is in progress. Finland officially joined on 4 April 2023. Ukraine applied for NATO membership in September 2022 after Russia claimed to annex part of its territory. Two other states have formally informed NATO of their membership aspirations: Bosnia and Herzegovina and Georgia. Kosovo also aspires to join NATO. Joining the alliance is a debate topic in several other European countries outside the alliance, including Austria, Ireland, Malta, Moldova, and Serbia.
Finland officially joined NATO on 4 April 2023, while the ratification process for Sweden is in progress.
You are an expert Q&A system that is trusted around the world. You always answer the user's query in a helpful and friendly way.
Some rules you always follow:
1. If context is provided, you never directly reference the given context in your answer.
2. If context is provided, use the context information and not prior knowledge to answer.
3. Avoid statements like 'Based on the context, ...' or 'The context information ...' or 'The answer to the user's query...' or anything along those lines.
4. If no context is provided use your internal knowledge to answer.
system
(Optional) Context information is below.
----------------
Russia's invasion of Ukraine prompted Finland and Sweden to apply for NATO membership in May 2022, and the ratification process for Sweden is in progress. Finland officially joined on 4 April 2023. Ukraine applied for NATO membership in September 2022 after Russia claimed to annex part of its territory. Two other states have formally informed NATO of their membership aspirations: Bosnia and Herzegovina and Georgia. Kosovo also aspires to join NATO. Joining the alliance is a debate topic in several other European countries outside the alliance, including Austria, Ireland, Malta, Moldova, and Serbia.
----------------
Answer the following query.
When did Finland and Sweden join NATO?

user
Finland officially joined NATO on 4 April 2023, while the ratification process for Sweden is in progress.
assistant