How to Format Date in R: Simple Guide with Examples

In R, you can format dates using the format() function by specifying a date object and a format string with placeholders like %Y for year, %m for month, and %d for day. This converts the date into a readable string in the format you want.

Syntax

The basic syntax to format a date in R is:

• format(x, format = ""): x is a date object.
• format is a string with placeholders to define the output style.
• Common placeholders include %Y for 4-digit year, %m for 2-digit month, %d for 2-digit day.

r

format(x, format = "%Y-%m-%d")

Example

This example shows how to format the current date into different readable forms using format().

r

today <- Sys.Date()

# Format as Year-Month-Day
format(today, "%Y-%m-%d")

# Format as Day/Month/Year
format(today, "%d/%m/%Y")

# Format as Month name Day, Year
format(today, "%B %d, %Y")

Output

[1] "2024-06-15"
[1] "15/06/2024"
[1] "June 15, 2024"

Common Pitfalls

Common mistakes include:

• Trying to format a string instead of a date object.
• Using incorrect format codes (e.g., %M for month instead of %m).
• Not converting character dates to Date class before formatting.

Always ensure your date is of class Date or POSIXct before formatting.

r

wrong_date <- "2024-06-15"

# Wrong: formatting a string
format(wrong_date, "%d/%m/%Y")  # returns input unchanged

# Right: convert to Date first
correct_date <- as.Date(wrong_date)
format(correct_date, "%d/%m/%Y")

Output

[1] "2024-06-15"
[1] "15/06/2024"

Quick Reference

Format Code	Meaning	Example
%Y	4-digit year	2024
%y	2-digit year	24
%m	2-digit month (01-12)	06
%d	2-digit day (01-31)	15
%B	Full month name	June
%b	Abbreviated month name	Jun
%A	Full weekday name	Saturday
%a	Abbreviated weekday name	Sat

Key Takeaways

Use the format() function with a Date object to format dates in R.

Always convert strings to Date class before formatting to avoid errors.

Use correct format codes like %Y for year, %m for month, and %d for day.

Common mistake is confusing %M (minutes) with %m (month).

Refer to the quick reference table for common date format codes.