x1 is the year / era of years indicated by PA (digit string) in calendar system x2
In the PA string, use PA4 digits as blanks to refer to time ranges. For example: "lo pasobixo'e cei'a" is the eighties (198X years), "lo pamuso'ixo'e cei'a" is the late 16th century (high 15XX years). x1 is an event or concept.