title: AWS RDS free tier: Is free usage reset every month?
body: <p>I'm using AWS RDS by free tier.</p>
  
  <p>I created a database in January, and created another databse in February. </p>
  
  <p>Today morning, I got a message that I was charged 12 dollars for overusage. </p>
  
  <p>I checked my AWS cost management, and found out that the cost for March so far is $0. </p>
  
  <p>I know that the free tier gives me 750 hours. </p>
  
  <p>But does it mean that I can use 750 hours every month? </p>
  
  <p>If so, can I use one database for free every month because 750/24 = 31?</p>
  
  <p>And did I get charged because I am activating two databases?</p>
  
  <p>Thanks.</p>