Is it OK to date a 4 year older?

Ilmanens answer is correct as far as it goes. If your parents agree with you dating, then it is legal. However, even with your parents and your consent, unless you are married, sexual contact is illegal.

Can you date someone 5 years older?

Yes, its correct that dating is not illegal. Thats because dating is not a specific act. Specific actions that are often associated with dating, like sex, can be illegal.