You may be wondering whether GDPR governs the handling of personal data which you collected before GDPR went into effect on May 25, 2018. The answer is both 'yes' and 'no', but mostly yes. It's also important to know that the UK incorporated the EU GDPR into UK law after Brexit, so you are still required to comply with the rules of GDPR if you are in the UK. In fact, the UK ICO (Information Commissioner's Office) says quite explicitly that "The provisions of the EU GDPR have been incorporated directly into UK law as the UK GDPR."