Regular Expressions 101

Explanation

Pro

1st Alternative^(?:(?:31(\/|-|\.)(?:0?[13578]|1[02]|(?:Jan|Mar|May|Jul|Aug|Oct|Dec)))\1|(?:(?:29|30)(\/|-|\.)(?:0?[1,3-9]|1[0-2]|(?:Jan|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec))\2))(?:(?:1[6-9]|[2-9]\d)?\d{2})$

^start of line

Non-Capturing Group(?:(?:31(\/|-|\.)(?:0?[13578]|1[02]|(?:Jan|Mar|May|Jul|Aug|Oct|Dec)))\1|(?:(?:29|30)(\/|-|\.)(?:0?[1,3-9]|1[0-2]|(?:Jan|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec))\2))

1st Alternative(?:31(\/|-|\.)(?:0?[13578]|1[02]|(?:Jan|Mar|May|Jul|Aug|Oct|Dec)))\1

Non-Capturing Group(?:31(\/|-|\.)(?:0?[13578]|1[02]|(?:Jan|Mar|May|Jul|Aug|Oct|Dec)))

31the literal text 31

Group 1(\/|-|\.)

1st Alternative\/

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

2nd Alternative-

-the literal - (45₁₀ / 55₈ / 2D₁₆)

3rd Alternative\.

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Non-Capturing Group(?:0?[13578]|1[02]|(?:Jan|Mar|May|Jul|Aug|Oct|Dec))

1st Alternative0?[13578]

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

Character Class[13578]

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

3the literal 3 (51₁₀ / 63₈ / 33₁₆)

5the literal 5 (53₁₀ / 65₈ / 35₁₆)

7the literal 7 (55₁₀ / 67₈ / 37₁₆)

8the literal 8 (56₁₀ / 70₈ / 38₁₆)

2nd Alternative1[02]

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[02]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

3rd Alternative(?:Jan|Mar|May|Jul|Aug|Oct|Dec)

Non-Capturing Group(?:Jan|Mar|May|Jul|Aug|Oct|Dec)

1st AlternativeJan

Janthe literal text Jan (case sensitive)

2nd AlternativeMar

Marthe literal text Mar (case sensitive)

3rd AlternativeMay

Maythe literal text May (case sensitive)

4th AlternativeJul

Julthe literal text Jul (case sensitive)

5th AlternativeAug

Augthe literal text Aug (case sensitive)

6th AlternativeOct

Octthe literal text Oct (case sensitive)

7th AlternativeDec

Decthe literal text Dec (case sensitive)

\1the text saved by group 1

2nd Alternative(?:(?:29|30)(\/|-|\.)(?:0?[1,3-9]|1[0-2]|(?:Jan|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec))\2)

Non-Capturing Group(?:(?:29|30)(\/|-|\.)(?:0?[1,3-9]|1[0-2]|(?:Jan|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec))\2)

Non-Capturing Group(?:29|30)

1st Alternative29

2nd Alternative30

Group 2(\/|-|\.)

Non-Capturing Group(?:0?[1,3-9]|1[0-2]|(?:Jan|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec))

\2the text saved by group 2

Non-Capturing Group(?:(?:1[6-9]|[2-9]\d)?\d{2})

$end of line

2nd Alternative^(?:29(\/|-|\.)(?:0?2|(?:Feb))\3(?:(?:(?:1[6-9]|[2-9]\d)?(?:0[48]|[2468][048]|[13579][26])|(?:(?:16|[2468][048]|[3579][26])00))))$

3rd Alternative^(?:0?[1-9]|1\d|2[0-8])(\/|-|\.)(?:(?:0?[1-9]|(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep))|(?:1[0-2]|(?:Oct|Nov|Dec)))\4(?:(?:1[6-9]|[2-9]\d)?\d{2})$

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

Match Information

Detailed match information will be displayed here automatically.

Quick Reference

25 tokens

Regular Expression

^(?:(?:31(\/|-|\.)(?:0?[13578]|1[02]|(?:Jan|Mar|May|Jul|Aug|Oct|Dec)))\1|(?:(?:29|30)(\/|-|\.)(?:0?[1,3-9]|1[0-2]|(?:Jan|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec))\2))(?:(?:1[6-9]|[2-9]\d)?\d{2})$|^(?:29(\/|-|\.)(?:0?2|(?:Feb))\3(?:(?:(?:1[6-9]|[2-9]\d)?(?:0[48]|[2468][048]|[13579][26])|(?:(?:16|[2468][048]|[3579][26])00))))$|^(?:0?[1-9]|1\d|2[0-8])(\/|-|\.)(?:(?:0?[1-9]|(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep))|(?:1[0-2]|(?:Oct|Nov|Dec)))\4(?:(?:1[6-9]|[2-9]\d)?\d{2})$

New

Right Ones
01/01/2000
1/1/2000
01/Jan/2000
31/01/2000
31/Jan/2000
31.Jan.2000
31-Jan-2000
28/02/2001
01/1/2000
01/Jan/2000
01/1/01
01/Jan/01
29/02/2000
29/Feb/2000

Wrong Ones
31/04/2000
29/Feb/2001
13/13/2000
30/Feb/2000
30/Mon/2000
32/01/2000
32/Jan/2000
01/01/2020 #1st Jan
07/03/2020 #3 July
12/2/2020 #2 December 
23/4/2020 #23 April

Extraction

Right Ones
01/01/2000
1/1/2000
01/Jan/2000
31/01/2000
31/Jan/2000
31.Jan.2000
31-Jan-2000
28/02/2001
01/1/2000
01/Jan/2000
01/1/01
01/Jan/01
29/02/2000
29/Feb/2000

Wrong Ones
31/04/2000
29/Feb/2001
13/13/2000
30/Feb/2000
30/Mon/2000
32/01/2000
32/Jan/2000
01/01/2020 #1st Jan
07/03/2020 #3 July
12/2/2020 #2 December 
23/4/2020 #23 April