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Regex for time hh:mm:ss

Regex for time hh:mm:ss

Time is a concept that is used to describe the duration of events or the progression of existence. It is often measured in units such as seconds, minutes, hours, days, and years. In this article let's understand how we can create a regex for time hh:mm:ss and how regex can be matched for a given time.

Regex (short for regular expression) is a powerful tool used for searching and manipulating text. It is composed of a sequence of characters that define a search pattern. Regex can be used to find patterns in large amounts of text, validate user input, and manipulate strings. It is widely used in programming languages, text editors, and command line tools.

Structure of a time hh:mm:ss

The time should have the following criteria and structure-

  • Then 2 digit hour
  • Then followed by a colon :
  • Then 2 digit minute
  • Then followed by a colon :
  • Then 2 digit second

Regex for checking if time hh:mm:ss is valid or not

Regular Expression for time hh:mm:ss is-

/^(?:[01]\d|2[0123]):(?:[012345]\d):(?:[012345]\d)$/gm

Test string examples for the above regex-

Input StringMatch Output
43:32does not match
32:11:43does not match
10:10:10matches
12:44:21matches
23:12:32matches

Here is a detailed explanation of the above regex-

/^(?:[01]\d|2[0123]):(?:[012345]\d):(?:[012345]\d)$/gm

^ asserts position at start of a line
Non-capturing group (?:[01]\d|2[0123])
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[0123]
2 matches the character 2 with index 5010 (3216 or 628) literally (case sensitive)
Match a single character present in the list below [0123]
0123 matches a single character in the list 0123 (case sensitive)
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
Non-capturing group (?:[012345]\d)
Match a single character present in the list below [012345]
012345 matches a single character in the list 012345 (case sensitive)
\d matches a digit (equivalent to [0-9])
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
Non-capturing group (?:[012345]\d)
Match a single character present in the list below [012345]
012345 matches a single character in the list 012345 (case sensitive)
\d matches a digit (equivalent to [0-9])
$ asserts position at the end of a line
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)

Hope this article was useful to check if the string is a valid time hh:mm:ss or not.