Date regex Python

Date regular expressions can be used to validate if a string has a valid date format and to extract a valid date from a string.

Simple date regex (DD/MM/YYYY)

Below is a simple regex to validate the string against a date format (D/M/YYYY or M/D/YYYY). This however does not guarantee that the date would be valid. You can also replace \\/ with a separator you need.

"^[0-9]{1,2}\\/[0-9]{1,2}\\/[0-9]{4}$"

Test it!

/^[0-9]{1,2}\/[0-9]{1,2}\/[0-9]{4}$/

True

False

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Example code in Python:

import re

# Validate date
date_pattern = "^[0-9]{1,2}\\/[0-9]{1,2}\\/[0-9]{4}$"
re.match(date_pattern, '12/12/2022') # Returns Match object

# Extract date from a string
date_extract_pattern = "[0-9]{1,2}\\/[0-9]{1,2}\\/[0-9]{4}"
re.findall(date_extract_pattern, 'I\'m on vacation from 1/18/2021 till 1/29/2021') # returns ['1/18/2021', '1/29/2021']

ISO 8061 date regex (e.g. 2021-11-04T22:32:47.142354-10:00)

The ISO 8061 is an international standard for exchanging and serializing date and time data. For validating the format of ISO 8061 date and time and for extracting it a following regular expression could be used:

"^(?:\\d{4})-(?:\\d{2})-(?:\\d{2})T(?:\\d{2}):(?:\\d{2}):(?:\\d{2}(?:\\.\\d*)?)(?:(?:-(?:\\d{2}):(?:\\d{2})|Z)?)$"

Test it!

/^(?:\d{4})-(?:\d{2})-(?:\d{2})T(?:\d{2}):(?:\d{2}):(?:\d{2}(?:\.\d*)?)(?:(?:-(?:\d{2}):(?:\d{2})|Z)?)$/

True

False

Enter a text in the input above to see the result

Example code in Python:

import re

# Validate ISO date
date_pattern = "^(?:\\d{4})-(?:\\d{2})-(?:\\d{2})T(?:\\d{2}):(?:\\d{2}):(?:\\d{2}(?:\\.\\d*)?)(?:(?:-(?:\\d{2}):(?:\\d{2})|Z)?)$"
re.match(date_pattern, '2021-11-04T22:32:47.142354-10:00') # Returns Match object

# Extract ISO date from a string
date_extract_pattern = "(?:\\d{4})-(?:\\d{2})-(?:\\d{2})T(?:\\d{2}):(?:\\d{2}):(?:\\d{2}(?:\\.\\d*)?)(?:(?:-(?:\\d{2}):(?:\\d{2})|Z)?)"
re.findall(date_extract_pattern, '2017-05-23T15:02:27Z | WARN | Record not found\n2018-05-23T15:02:28Z | WARN | Project with the id ’53’ was not found') # returns ['2017-05-23T15:02:27Z', '2018-05-23T15:02:28Z']

Test it!

True

False

Enter a text in the input above to see the result

Notes on date string regex validation

While there are some regular expressions that allow more complex date validations, it is usually better to validate dates using special date and time libraries. For example, in Python datetime package can be used for these purposes. In this case, the validation will look like this:

try:
  datetime.datetime.strptime("1-2-2022", '%d-%m-%Y')
  print("Correct date string")
except ValueError:
  print("Incorrect date string")

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