\s*a Unicode whitespace character, repeated any number of times
Non-Capturing Group(?:Jan(?:uary)?|Feb(?:ruary)?|Mar(?:ch)?|Apr(?:il)?|May|Jun(?:e)?|Jul(?:y)?|Aug(?:ust)?|Sep(?:tember)?|Oct(?:ober)?|Nov(?:ember)?|Dec(?:ember)?) 1st AlternativeJan(?:uary)? Janthe literal text Jan (case sensitive) Non-Capturing Group(?:uary)? ?repeats the group contents below at most once:
uarythe literal text uary (case sensitive) 2nd AlternativeFeb(?:ruary)? Febthe literal text Feb (case sensitive) Non-Capturing Group(?:ruary)? ?repeats the group contents below at most once:
ruarythe literal text ruary (case sensitive) 3rd AlternativeMar(?:ch)? Marthe literal text Mar (case sensitive) Non-Capturing Group(?:ch)? ?repeats the group contents below at most once:
chthe literal text ch (case sensitive) 4th AlternativeApr(?:il)? Aprthe literal text Apr (case sensitive) Non-Capturing Group(?:il)? ?repeats the group contents below at most once:
ilthe literal text il (case sensitive) Maythe literal text May (case sensitive) Junthe literal text Jun (case sensitive) Non-Capturing Group(?:e)? ?repeats the group contents below at most once:
ethe literal e (10110 / 1458 / 6516) (case sensitive)
Julthe literal text Jul (case sensitive) Non-Capturing Group(?:y)? ?repeats the group contents below at most once:
ythe literal y (12110 / 1718 / 7916) (case sensitive)
8th AlternativeAug(?:ust)? Augthe literal text Aug (case sensitive) Non-Capturing Group(?:ust)? ?repeats the group contents below at most once:
ustthe literal text ust (case sensitive) 9th AlternativeSep(?:tember)? Septhe literal text Sep (case sensitive) Non-Capturing Group(?:tember)? ?repeats the group contents below at most once:
temberthe literal text tember (case sensitive) 10th AlternativeOct(?:ober)? Octthe literal text Oct (case sensitive) Non-Capturing Group(?:ober)? ?repeats the group contents below at most once:
oberthe literal text ober (case sensitive) 11th AlternativeNov(?:ember)? Novthe literal text Nov (case sensitive) Non-Capturing Group(?:ember)? ?repeats the group contents below at most once:
emberthe literal text ember (case sensitive) 12th AlternativeDec(?:ember)? Decthe literal text Dec (case sensitive) Non-Capturing Group(?:ember)? ?repeats the group contents below at most once:
emberthe literal text ember (case sensitive) the literal (3210 / 408 / 2016)
\ba Unicode word boundary
Non-Capturing Group(?:[1-9]|[12]\d|3[01]) \ba Unicode word boundary
,the literal , (4410 / 548 / 2C16)
\s+a Unicode whitespace character, repeated at least once
\d{4}a Unicode decimal digit, repeated exactly 4 times
Slide the literal text Slide (case sensitive) \d+a Unicode decimal digit, repeated at least once
\s*a Unicode whitespace character, repeated any number of 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