\ba Unicode word boundary
\Sany character that is not Unicode whitespace
.*?any Unicode character (except for line terminators), repeated any number of times
Non-Capturing Group(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec) Janthe literal text Jan (case sensitive) Febthe literal text Feb (case sensitive) Marthe literal text Mar (case sensitive) Aprthe literal text Apr (case sensitive) Maythe literal text May (case sensitive) Junthe literal text Jun (case sensitive) Julthe literal text Jul (case sensitive) Augthe literal text Aug (case sensitive) Septhe literal text Sep (case sensitive) Octthe literal text Oct (case sensitive) Novthe literal text Nov (case sensitive) Decthe literal text Dec (case sensitive) \s+a Unicode whitespace character, repeated at least once
\d{1,2}a Unicode decimal digit, repeated between 1 and 2 times
\s+a Unicode whitespace character, repeated at least once
\d{4}a Unicode decimal digit, repeated exactly 4 times
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string