^start of line
Group 1(January|February|March|April|May|June|July|August|September|October|November|December) Januarythe literal text January (case insensitive) Februarythe literal text February (case insensitive) Marchthe literal text March (case insensitive) Aprilthe literal text April (case insensitive) Maythe literal text May (case insensitive) Junethe literal text June (case insensitive) Julythe literal text July (case insensitive) Augustthe literal text August (case insensitive) Septemberthe literal text September (case insensitive) Octoberthe literal text October (case insensitive) Novemberthe literal text November (case insensitive) Decemberthe literal text December (case insensitive) \s+any whitespace character, repeated at least once
\d{1,2}a digit, repeated between 1 and 2 times
,?optionally matches the literal , (4410 / 548 / 2C16)
\s+any whitespace character, repeated at least once
Non-Capturing Group(?:19|20) \d{2}a digit, repeated exactly 2 times
$end of line
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
i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters