deal-with-date-type.R

person <- c("Jack", "Rose", "Sam")
birthdates <- c("1999-03-01", "2000-12-23", "2000-09-20") # FORMAT: Year-Month-Day

class(birthdays)

people <- data.frame(name = person, birthdate = as.Date(birthdates))

class(people$birthdate)

birthdays <- as.Date(people$birthdate)

people <- data.frame(name = person, birthdate = birthdates)


people <- read.csv("people.csv")

people$birthdate = as.Date(people$birthdate)

people$birthdate = as.character(people$birthdate)

people$birthdate = format(people$birthdate, format="%d-%m-%Y")


# print current Date
print(Sys.Date())


# print current Date and Time
print(Sys.time())


# Date formats
print(format(Sys.Date(), format="%d")) # prints '08'

print(format(Sys.Date(), format="%A")) # prints 'Sunday'

print(format(Sys.Date(), format="%B")) # prints 'January'

print(format(Sys.Date(), format="%Y")) # prints '2023'

print(format(Sys.Date(), format="%B - %Y")) # prints 'January - 2023'


# time formats
print(format(Sys.time(), format="%H")) # prints '00'

print(format(Sys.time(), format="%M")) # prints '19'

print(format(Sys.time(), format="%X")) # prints '12:19:44 AM'

print(format(Sys.time(), format="%Z")) # prints '+04'


# current time in different cities
print(as.POSIXlt(Sys.time(), "Europe/Berlin"))

print(as.POSIXlt(Sys.time(), "Europe/Paris"))


# obtain all time and zones

tab <- file.path(R.home("share"), "zoneinfo", "zone1970.tab")
if(file.exists(tab)) {
  cols <- c("code", "coordinates", "TZ", "comments")
  tmp <- read.delim(file.path(R.home("share"), "zoneinfo", "zone1970.tab"),
                    header = FALSE, comment.char = "#", col.names = cols)
  if(interactive()) View(tmp)
  head(tmp, 10)
}


ymd("03-01-22") # 2003-01-22
ymd("11-11-21") # 2011-11-21
ymd("95-12-23") # 1995-12-23

dym() # day year month
dmy() # day month year 
mdy() # month day year 
myd() # month year day   
ymd() # year month day  
ydm() # year day month  


ydm_h("99-23-12-14") # "1999-12-23 14:00:00 UTC"
ydm_hm("99-23-12-14-23") # "1999-12-23 14:23:00 UTC"
ydm_hms("99-23-12-14-23-34") # "1999-12-23 14:23:34 UTC"


hm("14:23") # "14H 23M 0S"
hms("15:33:59") # "15H 33M 59S"


# difference between 2 dates
date1 <- as.Date("2023-01-21")
date2 <- as.Date("2023-02-24")

difftime(date2, date1, units = "secs") # 2937600 secs
difftime(date2, date1, units = "mins") # 48960 mins
difftime(date2, date1, units = "hours") # 816 hours
difftime(date2, date1, units = "days") # 34 days
difftime(date2, date1, units = "weeks") # 4.857143 weeks