Convert “unknown format” strings to datetime objects in Python

In this article, we are going to see how to convert the “Unknown Format” string to the DateTime object in Python.

Suppose, there are two strings containing dates in an unknown format and that format we don’t know. Here all we know is that both strings contain valid date-time expressions. By using the dateutil module containing a date parser that can parse date strings in many formats.

Let’s see some examples that illustrate this conversion in many ways:

Example 1: Convert “unknown format” strings to datetime objects

In the below example, the specified unknown format of date string “19750503T080120” is being parsed into a valid known format of the DateTime object.

Python3

# Python3 code to illustrate the conversion of
# "unknown format" strings to DateTime objects

# Importing parser from the dateutil.parser
import dateutil.parser as parser

# Initializing an unknown format date string
date_string = "19750503T080120"

# Calling the parser to parse the above
# specified unformatted date string
# into a datetime objects
date_time = parser.parse(date_string)

# Printing the converted datetime object
print(date_time)

Output:

1975-05-03 08:01:20

Example 2: Convert current date and time to datetime objects 

In the below example, the current date and time have been parsed into datetime object.

Python3

# Python3 code to illustrate the conversion of
# "unknown format" strings to DateTime objects

# Importing parser from the dateutil.parser and
# dt from datetime module
import dateutil.parser as parser
import datetime as dt

# Calling the now() function to
# return the current datetime
now = dt.datetime.now()

# Calling the isoformat() to return the
# current datetime in isoformat and print it
print(now.isoformat())

# Now calling the parser to parse the
# above returned isoformat datetime into
# a valid known format of datetime object
print(parser.parse(now.isoformat()))

Output:

2021-08-20T13:35:23.829488
2021-08-20 13:35:23.829488

Sometimes the DateTime strings can be ambiguous like 01-02-2003 could mean January 2 or February 1. To remove this ambiguity we have two parameters like dayfirst and yearfirst that are illustrated in the below examples.

Example 3: Convert specific unknown format to datetime objects

In the below example, the specified datetime is “10-09-2021”. The parse() has used the parameter dayfirst as True and returns the output as “2021-09-10 00:00:00” i.e 9th October of the 2021 year.

Python3

# Python3 code to illustrate the conversion of
# "unknown format" strings to DateTime objects

# Importing parser from the dateutil.parser
import dateutil.parser as parser

# Now parsing the "10-09-2021" datetime with
# dayfirst parameter
B = parser.parse("10-09-2021", dayfirst = True)

# Printing the parsed datetime
print(B)

Output:

2021-09-10 00:00:00