Date and Time

# My Journey into the Realm of Dates and Times in R
# As I navigate the intricacies of R, I find myself captivated by the elegance and precision with which it handles dates and times. It’s not just about processing; it feels like orchestrating a symphony of moments and intervals. When I invoke Sys.Date(), I am handed the present date as a Date object, a compact and structured representation of today. The simplicity with which I can access this information makes me appreciate how R encapsulates the complexity of temporal data into a user-friendly format.
# 
# Sys.time() enthralls me further, not just presenting a timestamp but embedding the nuances of both date and time into a POSIXct object. This encapsulation feels like holding a snapshot of the current moment in my hands, complete with all its contextual intricacies. When I convert this to numeric form using as.numeric(Sys.time()), I marvel at the transformation—watching abstract time turn into quantifiable seconds since the UNIX Epoch. It’s a moment where technology and time converge in a neat, calculable way.
# 
# Discovering my system’s time zone with Sys.timezone() makes me feel connected to the global web of timekeeping. Each location, each zone, part of a vast and meticulously coordinated system. The sheer breadth of time zones displayed by OlsonNames() is astounding—it’s like peeling back a layer to reveal the complex tapestry of how we, across the globe, mark time.
# 
# The end_of_month() function I create feels almost like a spell, taking any date and transforming it into the very last day of its month. It’s fascinating to watch R do the heavy lifting, adjusting and recalculating to land precisely on month-end. Similarly, when I work out the first day of any month with a simple cut operation, I find a strange satisfaction in how effortlessly I can reset any date to the start of its calendar cycle.
# 
# The most intriguing challenge comes when I build the move_months() function. This function is like a time navigator, allowing me to shift dates forward or backward by a precise number of months. Testing it with dates like the end of February or the 30th of April, I witness R’s graceful handling of the peculiarities of different month lengths. The function doesn’t just move through time; it respects the rules and quirks of the calendar, something that feels both logical and magical.
# 
# What fascinates me most is how these pieces interlock, creating a powerful toolkit for handling time. Each function, each operation, feels like a carefully crafted mechanism in a finely tuned clock, each contributing to a fuller, more nuanced understanding of temporal data. As I manipulate these date and time objects, I feel as though I’m gaining not just technical skills, but a deeper appreciation for the complexity and beauty of time itself.

# Current Date and Time

current_date <- Sys.Date()
current_date

## [1] "2024-11-03"

current_time <- Sys.time()
current_time

## [1] "2024-11-03 14:51:58 EST"

seconds_since_epoch <- as.numeric(Sys.time())
seconds_since_epoch

## [1] 1730663518

current_timezone <- Sys.timezone()
current_timezone

## [1] "America/New_York"

timezones <- str(OlsonNames())

##  chr [1:596] "Africa/Abidjan" "Africa/Accra" "Africa/Addis_Ababa" ...
##  - attr(*, "Version")= chr "2024a"

timezones

## NULL

# Load lubridate package
library(lubridate)

## 
## Attaching package: 'lubridate'

## The following objects are masked from 'package:base':
## 
##     date, intersect, setdiff, union

# Function to get the end of the month
end_of_month <- function(date) {
  date <- as.Date(date)
  ceiling_date(date, "month") - days(1)
}

# Example usage
dates_sequence <- seq(as.POSIXct("2010-03-15"), as.POSIXct("2010-08-15"), by = "months")
data.frame(before = dates_sequence, after = end_of_month(dates_sequence))

##       before      after
## 1 2010-03-15 2010-03-31
## 2 2010-04-15 2010-04-30
## 3 2010-05-15 2010-05-31
## 4 2010-06-15 2010-06-30
## 5 2010-07-15 2010-07-31
## 6 2010-08-15 2010-08-31

# Go to First Day of the Month

given_date <- as.Date("2019-07-25")
first_day_of_month <- as.POSIXlt(cut(given_date, "month"))
first_day_of_month

## [1] "2019-07-01 EDT"

# Move a Date a Number of Months

move_months <- function(date, num) {
  as.Date(mondate(date) + num)
}

# Install the mondate package
#install.packages("mondate")

# Load the package
library(mondate)

## 
## Attaching package: 'mondate'

## The following objects are masked from 'package:lubridate':
## 
##     as.difftime, day, month, quarter, year, ymd

## The following object is masked from 'package:base':
## 
##     as.difftime

# Function to move a date by a number of months
move_months <- function(date, num) {
  as.Date(mondate(date) + num)
}

# Test the function
move_months("2020-03-29", -1)

## [1] "2020-02-28"

move_months("2020-03-29", -2)

## [1] "2020-01-29"

move_months("2020-03-29", 2)

## [1] "2020-05-29"

move_months("2021-12-31", 2)

## [1] "2022-02-28"

move_months("2022-02-28", -2)

## [1] "2021-12-31"

move_months("2021-01-30", -2)

## [1] "2020-11-30"

move_months("2021-12-31", 2)

## [1] "2022-02-28"

library(knitr)
library(kableExtra)

# Data for the table
code_snippets <- data.frame(
  Description = c(
    "Current Date", "Current Time", "Seconds Since Epoch", "Current Timezone",
    "List Timezones", "End of the Month Function", "Example Date Sequence",
    "First Day of the Month", "Move Date by Months Function", "Test Move Date Function"
  ),
  Code = c(
    "current_date <- Sys.Date()\ncurrent_date",
    "current_time <- Sys.time()\ncurrent_time",
    "seconds_since_epoch <- as.numeric(Sys.time())\nseconds_since_epoch",
    "current_timezone <- Sys.timezone()\ncurrent_timezone",
    "timezones <- str(OlsonNames())\ntimezones",
    "end_of_month <- function(date) {\n  date <- as.Date(date)\n  ceiling_date(date, \"month\") - days(1)\n}",
    "dates_sequence <- seq(as.POSIXct(\"2010-03-15\"), as.POSIXct(\"2010-08-15\"), by = \"months\")\ndata.frame(before = dates_sequence, after = end_of_month(dates_sequence))",
    "given_date <- as.Date(\"2019-07-25\")\nfirst_day_of_month <- as.POSIXlt(cut(given_date, \"month\"))\nfirst_day_of_month",
    "move_months <- function(date, num) {\n  as.Date(mondate(date) + num)\n}",
    "move_months(\"2020-03-29\", -1)\nmove_months(\"2020-03-29\", -2)\nmove_months(\"2020-03-29\", 2)\nmove_months(\"2021-12-31\", 2)\nmove_months(\"2022-02-28\", -2)\nmove_months(\"2021-01-30\", -2)\nmove_months(\"2021-12-31\", 2)"
  )
)

# Create a colorful table
kable(code_snippets, "html", escape = FALSE) %>%
  kable_styling("striped", full_width = F, position = "center", bootstrap_options = c("hover", "condensed", "responsive")) %>%
  column_spec(1, bold = TRUE, color = "darkblue") %>%
  column_spec(2, width = "80%")

Description	Code
Current Date	current_date <- Sys.Date() current_date
Current Time	current_time <- Sys.time() current_time
Seconds Since Epoch	seconds_since_epoch <- as.numeric(Sys.time()) seconds_since_epoch
Current Timezone	current_timezone <- Sys.timezone() current_timezone
List Timezones	timezones <- str(OlsonNames()) timezones
End of the Month Function	end_of_month <- function(date) { date <- as.Date(date) ceiling_date(date, “month”) - days(1) }
Example Date Sequence	dates_sequence <- seq(as.POSIXct(“2010-03-15”), as.POSIXct(“2010-08-15”), by = “months”) data.frame(before = dates_sequence, after = end_of_month(dates_sequence))
First Day of the Month	given_date <- as.Date(“2019-07-25”) first_day_of_month <- as.POSIXlt(cut(given_date, “month”)) first_day_of_month
Move Date by Months Function	move_months <- function(date, num) { as.Date(mondate(date) + num) }
Test Move Date Function	move_months(“2020-03-29”, -1) move_months(“2020-03-29”, -2) move_months(“2020-03-29”, 2) move_months(“2021-12-31”, 2) move_months(“2022-02-28”, -2) move_months(“2021-01-30”, -2) move_months(“2021-12-31”, 2)

Date and Time

Avery Holloman

2024-11-03