\ba Unicode word boundary
Negative Lookahead(?!(?:18|19|20)\d{2}\b(?!\.\d)) Non-Capturing Group(?:18|19|20) \d{2}a Unicode decimal digit, repeated exactly 2 times
\ba Unicode word boundary
Negative Lookahead(?!\.\d) \.the literal . (4610 / 568 / 2E16)
\da Unicode decimal digit
\d*a Unicode decimal digit, repeated any number of times
\.?optionally matches the literal . (4610 / 568 / 2E16)
\d+a Unicode decimal digit, repeated at least once
\ba Unicode word boundary
g modifier: global. Finds all matches instead of stopping after the first