Working with Dates and Time

Dates and times in Excel are represented by real numbers, for example “Jan 1 2013 12:00 PM” is represented by the number 41275.5.

The integer part of the number stores the number of days since the epoch and the fractional part stores the percentage of the day.

A date or time in Excel is just like any other number. To display the number as a date you must apply an Excel number format to it. Here are some examples:

from xlsxwriter.workbook import Workbook

workbook = Workbook('date_examples.xlsx')
worksheet = workbook.add_worksheet()

# Widen column A for extra visibility.
worksheet.set_column('A:A', 30)

# A number to convert to a date.
number = 41333.5

# Write it as a number without formatting.
worksheet.write('A1', number)                # 41333.5

format2 = workbook.add_format({'num_format': 'dd/mm/yy'})
worksheet.write('A2', number, format2)       # 28/02/13

format3 = workbook.add_format({'num_format': 'mm/dd/yy'})
worksheet.write('A3', number, format3)       # 02/28/13

format4 = workbook.add_format({'num_format': 'd-m-yyyy'})
worksheet.write('A4', number, format4)       # 28-2-2013

format5 = workbook.add_format({'num_format': 'dd/mm/yy hh:mm'})
worksheet.write('A5', number, format5)       # 28/02/13 12:00

format6 = workbook.add_format({'num_format': 'd mmm yyyy'})
worksheet.write('A6', number, format6)       # 28 Feb 2013

format7 = workbook.add_format({'num_format': 'mmm d yyyy hh:mm AM/PM'})
worksheet.write('A7', number, format7)       # Feb 28 2008 12:00 PM

workbook.close()
_images/working_with_dates_and_times01.png

To make working with dates and times a little easier the XlsxWriter module provides a write_datetime() method to write dates in datetime.datetime format.

The datetime.datetime class is part of the standard Python datetime library.

There are many way to create a a datetime object but the most common is to use the datetime.strptime method:

date_time = datetime.strptime('2013-01-23', '%Y-%m-%d')

We also need to create and apply a number format to format the date:

date_format = workbook.add_format({'num_format': 'd mmmm yyyy'})
worksheet.write_datetime('A1', date_time, date_format)

# Displays "23 January 2013"

Here is a longer example that displays the same date in a several different formats:

from datetime import datetime
from xlsxwriter.workbook import Workbook

# Create a workbook and add a worksheet.
workbook = Workbook('datetimes.xlsx')
worksheet = workbook.add_worksheet()
bold = workbook.add_format({'bold': True})

# Expand the first columns so that the date is visible.
worksheet.set_column('A:B', 30)

# Write the column headers.
worksheet.write('A1', 'Formatted date', bold)
worksheet.write('B1', 'Format', bold)

# Create a datetime object to use in the examples.

date_time = datetime.strptime('2013-01-23 12:30:05.123',
                              '%Y-%m-%d %H:%M:%S.%f')

# Examples date and time formats.
date_formats = (
    'dd/mm/yy',
    'mm/dd/yy',
    'dd m yy',
    'd mm yy',
    'd mmm yy',
    'd mmmm yy',
    'd mmmm yyy',
    'd mmmm yyyy',
    'dd/mm/yy hh:mm',
    'dd/mm/yy hh:mm:ss',
    'dd/mm/yy hh:mm:ss.000',
    'hh:mm',
    'hh:mm:ss',
    'hh:mm:ss.000',
)

# Start from first row after headers.
row = 1

# Write the same date and time using each of the above formats.
for date_format_str in date_formats:

    # Create a format for the date or time.
    date_format = workbook.add_format({'num_format': date_format_str,
                                      'align': 'left'})

    # Write the same date using different formats.
    worksheet.write_datetime(row, 0, date_time, date_format)

    # Also write the format string for comparison.
    worksheet.write_string(row, 1, date_format_str)

    row += 1
_images/working_with_dates_and_times02.png

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