Regex for yyyy-mm-dd hh:mm:ss
A date is a specific day or time period, often given as a combination of a month, date, and year. In this article let's understand how we can create a regex for date yyyymmdd and how regex can be matched for a given date.
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 yyyymmdd
The date should have the following criteria and structure-
- Date is dd - where d is a digit
- Month is mm - where m is a digit
- Year is yyyy - where y is a digit
- Supported date format is yyyymmdd
Simple regex for checking if yyyy-mm-dd is valid or not
/^[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1])$/gm
Test string examples for the above regex-
| Input String | Match Output |
|---|---|
| 33-43-12 | does not match |
| 2022-12-12 | matches |
| 332-122-21 | does not match |
| 2992-12-12 | matches |
Here is a detailed explanation of the above regex-
/^[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1])$/gm
Match a single character present in the list below [0-9]
{4} matches the previous token exactly 4 times
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case insensitive)
- matches the character - with index 4510 (2D16 or 558) literally (case insensitive)
1st 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 insensitive)
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 insensitive)
2nd Alternative 1[0-2]
1 matches the character 1 with index 4910 (3116 or 618) literally (case insensitive)
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 insensitive)
- matches the character - with index 4510 (2D16 or 558) literally (case insensitive)
2nd Capturing Group (0[1-9]|[1-2][0-9]|3[0-1])
1st Alternative 0[1-9]
0 matches the character 0 with index 4810 (3016 or 608) literally (case insensitive)
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 insensitive)
2nd Alternative [1-2][0-9]
Match a single character present in the list below [1-2]
1-2 matches a single character in the range between 1 (index 49) and 2 (index 50) (case insensitive)
Match a single character present in the list below [0-9]
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case insensitive)
3rd Alternative 3[0-1]
3 matches the character 3 with index 5110 (3316 or 638) literally (case insensitive)
Match a single character present in the list below [0-1]
0-1 matches a single character in the range between 0 (index 48) and 1 (index 49) (case insensitive)
Global pattern flags
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
g modifier: global. All matches (don't return after first match)
Hope this article was useful to check if the string is a valid yyyymmdd name or not.
