The greatest() expression reduces to either the current year (year + 0) or the next year (year + 1) by taking the sign of the difference in start/end days. This allows me to derive an end date, such as:
Dec 22, 1900 to Mar 22, 1901
Then I check if the measured date falls between those two dates.
The expression might not be correct as I'm still quite new to PostgreSQL's syntax.
Dave
