Most units of measurement in the world of Might & Fealty are derived from human or daily-life base values, and the metric system has not yet been invented. This is mostly flavor because you as a player never need to do any calculations with these numbers, so it doesn't matter if the units are confusing, as they often were in the real world middle ages.
One advantage of our fictional world is that everyone uses the same measurements, instead of, say, the word "mile" referring to anything from 578 m (China) to 8888 m (Baden, Germany). Also, if you hover the mouse over any distance value, the game will show you the distance in other values (miles in yards, etc).
People in Might & Fealty use the yard as their unit of measurement for short distances, with a yard being almost the same as a metre (0.9144 metres, to be exact).
For medium distances, the world of Might & Fealty uses the mile as a unit of measurement. The mile used in Might & Fealty is the nautical mile of 1,852 metres which is used in the real world today in international law and treaties.
For larger distances beyond a few miles, the league is the common unit of measurement. For purely sentimental reasons, Might & Fealty uses the Hamburg League, also known as the Landesmeile or German state mile, which is equivalent to 7,532.5 metres.
Leagues are not abbreviated. If you can travel for a day, you can write a whole word.
The hectare is used mostly be peasants to measure small areas and covers 100m by 100m.
For medium-sized areas, the square mile is used, which is (of course) one mile squared, equivalent to about 343 hectares.
Extensive areas such as large realms, are measures in square leagues, where one square league is equivalent to about 16.54 square miles.
The game is set in accelerated realtime, meaning one day in our world equals four days in the game (one day in Might & Fealty happens every 6 hours).
The world of Might & Fealty also has its own calendar, which is a bit simpler than most earthly ones:
The typical shorthand notation for dates within the game is year-week-day, so 1-14-3 is the 3rd day of the 14th week in the 1st year.