datetime.toordinal() is a simple method used to manipulate the objects of DateTime class. It returns proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1. The function returns the ordinal value for the given DateTime object.

If January 1 of year 1 has ordinal number 1 then, January 2 year 1 will have ordinal number 2, and so on.

Syntax: 

datetimeObj.toordinal()

Parameters: None

Returns: Ordinal Value

Given below are some implementations for the same.

Example 1: Use datetime.toordinal() function to return the Gregorian ordinal for the given datetime object using date.today() class of datetime module.

# Python3 code to demonstrate
# Getting Ordinal value using
# toordinal().

# importing datetime module for today()
import datetime

# using date.today() to get todays date
dateToday = datetime.date.today()

# Using toordinal() to generate ordinal value.
toOrdinal = dateToday.toordinal()

# Prints Ordinal Value of Todays Date.
print(f"Ordinal of date {dateToday} is {toOrdinal}")

Ordinal of date 2021-08-03 is 738005

Note: Attributes of DateTime class should be in given range otherwise it will show a ValueError

Example 2: Example to show the parameters needs to be in the range

# importing datetime class
from datetime import datetime

# Creating an instance of datetime.
dateIs = datetime(189, 0, 0)

# Using toordinal() method
toOrdinal = dateIs.toordinal()
print(f"Ordinal value of Earliest Datetime {dateIs} is {toOrdinal}")

Output:

Traceback (most recent call last):

  File "/home/2ecd5f27fbc894dc8eeab3aa6559c7ab.py", line 5, in <module>

    dateIs = datetime(189,0,0)

ValueError: month must be in 1..12

Example 3: Use datetime.toordinal() function to return the Gregorian ordinal for the given DateTime object.

# importing datetime class
from datetime import datetime

# Creating an instance of datetime.
dateIs = datetime(1, 1, 1, 0, 0, 0, 0)

# Using toordinal() method
toOrdinal = dateIs.toordinal()
print(f"Ordinal value of Earliest Datetime {dateIs} is {toOrdinal}")

print()

dateIs = datetime(9999, 12, 31, 23, 59, 59)
toOrdinal = dateIs.toordinal()
print(f"Ordinal value of Latemost Datetime {dateIs} is {toOrdinal}")

Output:

Ordinal value of Earliest Datetime 0001-01-01 00:00:00 is 1

Ordinal value of Latemost Datetime 9999-12-31 23:59:59 is 3652059