Unless it is too personal, you can tell the real reason for which you were out of job. There is no need to concoct the reasons.
Your worry of skills getting outdated is little unfounded. Service functions of the HR department which earlier was called as personnel management has remained as it. Some changes in labour laws have taken place. You can update on these on your own. The hardcore part of the HR also has remained as it is. HR's role in this function lies in improving relations with the employees or improve their engagement with the organisation. It cannot become outdated in 2-3 years.
Therefore, go ahead and start applying for the jobs. If you are MBA or have done some course in HR then open your books and start reading. Refresh your knowledge!
All the best!
13th December 2018 From India, Bangalore