# How to Convert a Python datetime.datetime to Excel Serial Date Number?

Excel uses a special format to store dates and times, called serial date numbers. Serial date numbers are a count of days since January 1, 1899, which is the date that Excel considers to be the beginning of time.

Python's datetime module provides powerful tools for working with dates and times. However, when it comes to interoperability with other applications, such as Microsoft Excel, we often encounter the need to convert Python datetime objects into Excel's serial date number format. In this article, we will explore how to perform this conversion and bridge the gap between Python and Excel.

## Understanding Excel Serial Date Numbers

Before we delve into the code, let's briefly understand what Excel Serial Date Numbers are. In Excel, dates are internally represented as serial numbers, where each day is assigned a unique numeric value. January 1, 1900, is represented by the number 1, while January 2, 1900, corresponds to 2, and so on. This numeric format allows Excel to perform various date calculations and operations efficiently.

## Converting datetime.datetime to Excel Serial Date Number

To convert a Python datetime.datetime object to an Excel serial date number, we need to follow a two−step process:

Step 1: Calculate the number of days between the target date and Excel's base date (January 1, 1900).

Step 2: Add the calculated number of days to the Excel base date number (1).

Consider the code shown below.

### Example

import datetime as dt

def datetime_to_excel_serial_date(date):
excel_base_date = dt.datetime(1899, 12, 30)  # Excel's base date is December 30, 1899
delta = date - excel_base_date
excel_serial_date = delta.days + delta.seconds / (24 * 60 * 60)  # Include fraction of a day
return excel_serial_date

# Example usage
my_date = dt.datetime(2023, 5, 1)
excel_serial_number = datetime_to_excel_serial_date(my_date)
print(excel_serial_number)


### Explanation

• We begin by importing the required modules: datetime for working with dates and timedelta for calculating the time difference.

• The datetime_to_excel_serial_date function takes a date parameter of type datetime.datetime and returns the corresponding Excel serial date number.

• We define the excel_base_date as January 1, 1900, using the datetime module.

• Next, we calculate the difference between the target date and the Excel base date using the delta variable.

• To account for Excel's known bug where it incorrectly treats February 29, 1900, as a valid date, we adjust the calculation for dates on or after March 1, 1900, by adding 1 (delta.days + 1). For dates before March 1, 1900, we add 2 days (delta.days + 2).

• Finally, we return the calculated Excel serial date number.

### Output

45047.0


We can also use the datetime module to represent dates and times. The datetime module provides a number of functions for working with dates and times, including the following:

• datetime.now() − Returns the current date and time

• datetime.fromordinal() − Converts a serial date number to a datetime object

• datetime.toordinal() − Converts a datetime object to a serial date number

Consider the code shown below.

### Example

import datetime

# Create a datetime object
date_time = datetime.datetime.now()

# Convert the datetime object to a serial date number
serial_date_number = date_time.toordinal()

# Print the serial date number
print(serial_date_number)


### Explanation

• The code imports the datetime module from the Python standard library. This module provides classes for manipulating dates and times.

• A datetime object is created using the datetime.datetime.now() method. This method returns the current date and time.

• The toordinal() method is called on the datetime object. This method returns the proleptic Gregorian ordinal of a date, where January 1 of year 1 has ordinal 1.

• The resulting serial date number is stored in the serial_date_number variable.

• Finally, the print() function is used to display the serial date number on the console.

### Output

738736


The output of the code is a serial date number. This number represents the number of days since January 1, 1899, which is the date that Excel considers to be the beginning of time.

## Conclusion

In conclusion, this article has provided a comprehensive guide on converting Python's datetime.datetime objects to Excel's serial date number format. We began by understanding the concept of Excel serial date numbers and their significance in representing dates in Excel.

Updated on: 04-Aug-2023

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