Every 90 days Magento 2 will ask you to reset your admin password, which can be a nuisance when working on your local environment.  The picture below shows where Magento checks to see if your password has expired.  The admin_passwords table has a field called last_updated, which is the last time your password was changed.  So, the picture below shows that if last_updated plus getAdminPasswordLifetime (which is the system config value for admin/security/password_lifetime * number of seconds in a day) is greater than the current time, then Magento will ask you to reset your password.

If you would like Magento never to ask you to reset your password, then, run the query below.  This query will create the node admin/security/password_lifetime in your database’s core_config_data table — or update it if it doesn’t exist — and set its value to 10 million.  Now, Magento will never ask you to reset your admin password again.  Lastly, run the flush and clean cache commands, and you are all set!

Query to Fix the Issue:

INSERT INTO core_config_data (path,value) VALUES (‘admin/security/password_lifetime’,10000000)
ON DUPLICATE KEY UPDATE path=’admin/security/password_lifetime’,value=10000000;