regex101: DDMMMYYYY w/Leap Year Check

Pro

^start of line

Group 1((0?[1-9]|[12][0-9]|3[01])(Jan|JAN|Mar|MAR|May|MAY|Jul|JUL|Aug|AUG|Oct|OCT|Dec|DEC)([0-9][0-9][0-9][0-9])|(0?[1-9]|[12][0-9]|30)(Apr|APR|Jun|JUN|Sep|SEP|Nov|NOV)([0-9][0-9][0-9][0-9])|(0?[1-9]|1[0-9]|2[0-8])(Feb|FEB)([0-9][0-9][0-9][0-9])|(29)(Feb|FEB)([0-9][0-9])([02468][048]|[13579][26]))

1st Alternative(0?[1-9]|[12][0-9]|3[01])(Jan|JAN|Mar|MAR|May|MAY|Jul|JUL|Aug|AUG|Oct|OCT|Dec|DEC)([0-9][0-9][0-9][0-9])

Group 2(0?[1-9]|[12][0-9]|3[01])

1st Alternative0?[1-9]

0?optionally matches the literal 0 (48₁₀ / 60₈ / 30₁₆)

Character Class[1-9]

1-9one character from 1 (49₁₀) to 9 (57₁₀)

2nd Alternative[12][0-9]

Character Class[12]

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-9]

0-9one character from 0 (48₁₀) to 9 (57₁₀)

3rd Alternative3[01]

3the literal 3 (51₁₀ / 63₈ / 33₁₆)

Character Class[01]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Group 3(Jan|JAN|Mar|MAR|May|MAY|Jul|JUL|Aug|AUG|Oct|OCT|Dec|DEC)

1st AlternativeJan

Janthe literal text Jan (case sensitive)

2nd AlternativeJAN

JANthe literal text JAN (case sensitive)

3rd AlternativeMar

Marthe literal text Mar (case sensitive)

4th AlternativeMAR

MARthe literal text MAR (case sensitive)

5th AlternativeMay

Maythe literal text May (case sensitive)

6th AlternativeMAY

MAYthe literal text MAY (case sensitive)

7th AlternativeJul

Julthe literal text Jul (case sensitive)

8th AlternativeJUL

JULthe literal text JUL (case sensitive)

9th AlternativeAug

Augthe literal text Aug (case sensitive)

10th AlternativeAUG

AUGthe literal text AUG (case sensitive)

11th AlternativeOct

Octthe literal text Oct (case sensitive)

12th AlternativeOCT

OCTthe literal text OCT (case sensitive)

13th AlternativeDec

Decthe literal text Dec (case sensitive)

14th AlternativeDEC

DECthe literal text DEC (case sensitive)

Group 4([0-9][0-9][0-9][0-9])

2nd Alternative(0?[1-9]|[12][0-9]|30)(Apr|APR|Jun|JUN|Sep|SEP|Nov|NOV)([0-9][0-9][0-9][0-9])

3rd Alternative(0?[1-9]|1[0-9]|2[0-8])(Feb|FEB)([0-9][0-9][0-9][0-9])

4th Alternative(29)(Feb|FEB)([0-9][0-9])([02468][048]|[13579][26])

$end of line

Global pattern flags

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

25 tokens

Regular Expression

^((0?[1-9]|[12][0-9]|3[01])(Jan|JAN|Mar|MAR|May|MAY|Jul|JUL|Aug|AUG|Oct|OCT|Dec|DEC)([0-9][0-9][0-9][0-9])|(0?[1-9]|[12][0-9]|30)(Apr|APR|Jun|JUN|Sep|SEP|Nov|NOV)([0-9][0-9][0-9][0-9])|(0?[1-9]|1[0-9]|2[0-8])(Feb|FEB)([0-9][0-9][0-9][0-9])|(29)(Feb|FEB)([0-9][0-9])([02468][048]|[13579][26]))$

New

1Jan2018 abcd
1Jan18
01Jan18
1Jan2018
01Jan2018
31Jan2018
31jan2018
31jAN2018
31JaN2018
31JAn2018
31JAN2018
28Feb2018
29Feb2018
29Feb2020
31Mar2018
30Apr2018
31Apr2018
31May2018
30Jun2018
31Jun2018
31Jul2018
31Aug2018
30Sep2018
31Sep2018
31Oct2018
30Nov2018
31Nov2018
31Dec2018