Date & Time in R – Introduction

Date

Let us begin by looking at the current date and time. Sys.Date() and today() will return the current date.

Sys.Date()
## [1] "2021-02-03"
lubridate::today()
## [1] "2021-02-03"

Time

Sys.time() and now() return the date, time and the timezone. In now(), we can specify the timezone using the tzone argument.

Sys.time()
## [1] "2021-02-03 18:54:23 IST"
lubridate::now()
## [1] "2021-02-03 18:54:23 IST"
lubridate::now(tzone = "UTC")
## [1] "2021-02-03 13:24:23 UTC"

AM or PM?

am() and pm() allow us to check whether date/time occur in the AM or PM? They return a logical value i.e. TRUE or FALSE

lubridate::am(now())
## [1] FALSE
lubridate::pm(now())
## [1] TRUE

Leap Year

We can also check if the current year is a leap year using leap_year().

Sys.Date()
## [1] "2021-02-03"
lubridate::leap_year(Sys.Date())
## [1] FALSE

Summary

Your Turn

• get current date
• get current time
• check whether the time occurs in am or pm?
• check whether the following years were leap years
  • 2018
  • 2016

Data

transact <- readr::read_csv('https://raw.githubusercontent.com/rsquaredacademy/datasets/master/transact.csv')
## # A tibble: 2,466 x 3
##    Invoice    Due        Payment   
##    <date>     <date>     <date>    
##  1 2013-01-02 2013-02-01 2013-01-15
##  2 2013-01-26 2013-02-25 2013-03-03
##  3 2013-07-03 2013-08-02 2013-07-08
##  4 2013-02-10 2013-03-12 2013-03-17
##  5 2012-10-25 2012-11-24 2012-11-28
##  6 2012-01-27 2012-02-26 2012-02-22
##  7 2013-08-13 2013-09-12 2013-09-09
##  8 2012-12-16 2013-01-15 2013-01-12
##  9 2012-05-14 2012-06-13 2012-07-01
## 10 2013-07-01 2013-07-31 2013-07-26
## # ... with 2,456 more rows

We will explore more about reading data sets with date/time columns after learning how to parse date/time. We have shared the code for reading the data sets used in the practice questions both in the Learning Management System as well as in our GitHub repo.

Data Dictionary

The data set has 3 columns. All the dates are in the format (yyyy-mm-dd).

In the case study, we will try to answer a few questions we have about the transact data.

• extract date, month and year from Due
• compute the number of days to settle invoice
• compute days over due
• check if due year is a leap year
• check when due day in february is 29, whether it is a leap year
• how many invoices were settled within due date
• how many invoices are due in each quarter

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