Regular Expressions 101

1st Alternative^$

^start of line

$end of line

2nd Alternative^(?!00:00$)(([01][0-9])|(2[0-3])):[0-5][0-9]$

^start of line

Negative Lookahead(?!00:00$)

00:00the literal text 00:00

$end of line

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

1st Alternative([01][0-9])

Group 2([01][0-9])

Character Class[01]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-9]

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

2nd Alternative(2[0-3])

Group 3(2[0-3])

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-3]

0-3one character from 0 (48₁₀) to 3 (51₁₀)

:the literal : (58₁₀ / 72₈ / 3A₁₆)

Character Class[0-5]

0-5one character from 0 (48₁₀) to 5 (53₁₀)

Character Class[0-9]

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

$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

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Search reference

Regular Expression

^$|^(?!00:00$)(([01][0-9])|(2[0-3])):[0-5][0-9]$

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