FDP Calculator is a tool that helps you planning Crew duties with accordance to Flight Time Limitations.
As you can see in the screenshot, it takes the following values into consideration:
Basic FDP lenght calculation is based on the Max FDP table implemented in Leon (as in an operator OM-7). Basic duty includes reporting and post-flight duty times and is based on MAX FDP.
Latest time on blocks is the latest time allowed for Block On. This is Basic duty reduced by the check out time.