Regular Expressions 101

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/
^(0[1-9]|1\d|2[0-8]|29(?=-\d\d-(?!1[01345789]00|2[1235679]00)\d\d(?:[02468][048]|[13579][26]))|30(?!-02)|31(?=-0[13578]|-1[02]))-(0[1-9]|1[0-2])-([12]\d{3}) ([01]\d|2[0-3]):([0-5]\d):([0-5]\d)$
/
^ asserts position at start of the string
1st Capturing Group
(0[1-9]|1\d|2[0-8]|29(?=-\d\d-(?!1[01345789]00|2[1235679]00)\d\d(?:[02468][048]|[13579][26]))|30(?!-02)|31(?=-0[13578]|-1[02]))
1st Alternative
0[1-9]
0 matches the character 0 with index 4810 (3016 or 608) literally (case sensitive)
Match a single character present in the list below
[1-9]
1-9 matches a single character in the range between 1 (index 49) and 9 (index 57) (case sensitive)
2nd Alternative
1\d
1 matches the character 1 with index 4910 (3116 or 618) literally (case sensitive)
\d matches a digit (equivalent to [0-9])
3rd Alternative
2[0-8]
2 matches the character 2 with index 5010 (3216 or 628) literally (case sensitive)
Match a single character present in the list below
[0-8]
0-8 matches a single character in the range between 0 (index 48) and 8 (index 56) (case sensitive)
4th Alternative
29(?=-\d\d-(?!1[01345789]00|2[1235679]00)\d\d(?:[02468][048]|[13579][26]))
29
matches the characters 29 literally (case sensitive)
Positive Lookahead
(?=-\d\d-(?!1[01345789]00|2[1235679]00)\d\d(?:[02468][048]|[13579][26]))
Assert that the Regex below matches
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
Negative Lookahead
(?!1[01345789]00|2[1235679]00)
Assert that the Regex below does not match
1st Alternative
1[01345789]00
1 matches the character 1 with index 4910 (3116 or 618) literally (case sensitive)
Match a single character present in the list below
[01345789]
01345789
matches a single character in the list 01345789 (case sensitive)
00
matches the characters 00 literally (case sensitive)
2nd Alternative
2[1235679]00
2 matches the character 2 with index 5010 (3216 or 628) literally (case sensitive)
Match a single character present in the list below
[1235679]
1235679
matches a single character in the list 1235679 (case sensitive)
00
matches the characters 00 literally (case sensitive)
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
Non-capturing group
(?:[02468][048]|[13579][26])
1st Alternative
[02468][048]
Match a single character present in the list below
[02468]
02468
matches a single character in the list 02468 (case sensitive)
Match a single character present in the list below
[048]
048
matches a single character in the list 048 (case sensitive)
2nd Alternative
[13579][26]
Match a single character present in the list below
[13579]
13579
matches a single character in the list 13579 (case sensitive)
Match a single character present in the list below
[26]
26
matches a single character in the list 26 (case sensitive)
5th Alternative
30(?!-02)
30
matches the characters 30 literally (case sensitive)
Negative Lookahead
(?!-02)
Assert that the Regex below does not match
-02
matches the characters -02 literally (case sensitive)
6th Alternative
31(?=-0[13578]|-1[02])
31
matches the characters 31 literally (case sensitive)
Positive Lookahead
(?=-0[13578]|-1[02])
Assert that the Regex below matches
1st Alternative
-0[13578]
-0
matches the characters -0 literally (case sensitive)
Match a single character present in the list below
[13578]
13578
matches a single character in the list 13578 (case sensitive)
2nd Alternative
-1[02]
-1
matches the characters -1 literally (case sensitive)
Match a single character present in the list below
[02]
02
matches a single character in the list 02 (case sensitive)
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
2nd Capturing Group
(0[1-9]|1[0-2])
1st Alternative
0[1-9]
0 matches the character 0 with index 4810 (3016 or 608) literally (case sensitive)
Match a single character present in the list below
[1-9]
1-9 matches a single character in the range between 1 (index 49) and 9 (index 57) (case sensitive)
2nd Alternative
1[0-2]
1 matches the character 1 with index 4910 (3116 or 618) literally (case sensitive)
Match a single character present in the list below
[0-2]
0-2 matches a single character in the range between 0 (index 48) and 2 (index 50) (case sensitive)
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
3rd Capturing Group
([12]\d{3})
Match a single character present in the list below
[12]
12
matches a single character in the list 12 (case sensitive)
\d
matches a digit (equivalent to [0-9])
{3} matches the previous token exactly 3 times
matches the character with index 3210 (2016 or 408) literally (case sensitive)
4th Capturing Group
([01]\d|2[0-3])
1st Alternative
[01]\d
Match a single character present in the list below
[01]
01
matches a single character in the list 01 (case sensitive)
\d matches a digit (equivalent to [0-9])
2nd Alternative
2[0-3]
2 matches the character 2 with index 5010 (3216 or 628) literally (case sensitive)
Match a single character present in the list below
[0-3]
0-3 matches a single character in the range between 0 (index 48) and 3 (index 51) (case sensitive)
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
5th Capturing Group
([0-5]\d)
Match a single character present in the list below
[0-5]
0-5 matches a single character in the range between 0 (index 48) and 5 (index 53) (case sensitive)
\d matches a digit (equivalent to [0-9])
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
6th Capturing Group
([0-5]\d)
Match a single character present in the list below
[0-5]
0-5 matches a single character in the range between 0 (index 48) and 5 (index 53) (case sensitive)
\d matches a digit (equivalent to [0-9])
$ asserts position at the end of the string
Your regular expression does not match the subject string.

Regular Expression
No Match

/
/

Test String