Q:

What does "living 15 Rich. II" mean for the year an ancestor was alive in England?

What does "living 15 Rich. II" mean for the year an ancestor was alive in England?
This is a notation used in the British Roots of Maryland Families II by Robert W. Barnes regarding the Bysshe Family.
It also says another ancestor was "living 14 Hen. V and 36 Hen. VI." I thought it may mean the ancestor was living in 1414 since Henry V was ruling at during that year and 1436 since Henry VI was ruling during that year. However Richard II ruled between 1377-1399 so I can't figure out what the 15 in "living 15 Rich. II" means.

A:

This format of this date is called a Regnal year. It was commonly used in England, and is simply the number of years into the reign of the named monarch. A list of regnal years of English monarchs is available on Wikipedia.
Thus:

15 Rich. II = 1392
14 Hen. V is an error, since Henry V only reigned 10 years
36 Hen. VI = 1458

My favourite resource for calculating regnal years is this regnal year calculator. There are many other similar calculators available.
Be careful when making calculations, because regnal years get complicated, not least because for much of the history of the British monarchy the year started on March 25th rather than January 1st. Also, some monarchs had several regnal years corresponding to the same year. For example, James VI of Scotland was already in the 36th year of his reign of Scotland when he became James I, King of England.
Just for fun, today (2 Jul 2017) would be written as 66 Eliz. II. 

A:

Normally that notation means the year of the reign - starting with 1 Henry N or whatever. Except that the notation doesn't work for Henry V who only reigned 1413-1422.... 
So either I'm wrong or the transcript is wrong.... 
Feel free to edit this answer if it's useful. 

