从R中的当前日期获取上个月的开始日期和结束日期

Question

Is there any easy way for getting start date and end date of previous month from the current date in R?

I have only the current date. From it, i want to get the previous month, start date of previous month, end date of previous month.

currentDate<-Sys.Date() #return today's date as "2012-11-07"

I want the previous month start date as 2012-10-01 and end date as 2012-10-31 from today's date.

Answer 1

A number of packages have handy date functions, but to roll your own:

A start of month function:

som <- function(x) {
  as.Date(format(x, "%Y-%m-01"))
}

and an end of month function (although you won't need this here):

eom <- function(x) {
  som(som(x) + 35) - 1
}

That should get you going. For example, to get the end of the previous month:

som(Sys.Date()) - 1
[1] "2012-10-31"

and the start of the month:

som(som(Sys.Date()) - 1)
[1] "2012-10-01"

Answer 2

Using lubridate it's a piece of cake:

library(lubridate)
floor_date(Sys.Date() - months(1), "month")

There is a plenty of good libraries in R. Seems like everything you need is already created.

UPDATED version:

library(lubridate)
floor_date(as.Date("2011-03-29"), "month") - months(1)

This one is corrected to work well with the 29th of march.

Answer 3

You can use the library lubridate , which is very good at doing date arithmetic.

library(lubridate)

currentDate <-Sys.Date()
# end of previous month:
eopm <- currentDate - days(day(currentDate))
# [1] "2012-10-31"

# start of previous month:
sopm <- currentDate - days(day(currentDate))
sopm <- sopm - days(day(sopm) - 1)
# [1] "2012-10-01"

Answer 4

Another option with lubridate package is to use the rollback function, that as the description says, do exactly that.

rollback changes a date to the last day of the previous month or to the first day of the month. Optionally, the new date can retain the same hour, minute, and second information.

library(lubridate)

currentDate <- Sys.Date()

end_last_month <- rollback(currentDate)

init_last_month <- rollback(end_last_month, roll_to_first = TRUE)

Answer 5

Previous Month Start Date:

format(Sys.Date() - 30, '%Y-%m-01')

Previous Month End Date:

as.Date(format(Sys.Date(), '%Y-%m-01')) - 1

Answer 6

use timeperiodsR for get start and end date of any period.

# install.packages("timeperiodsR")
timeperiodsR::previous_month()

Answer 7

This solution takes into account the fact that when you subtract 30 days from "2022-03-01" you arrive at January not February.

# Get end date of previous month
end <- (as.Date(format(Sys.Date(), "%Y-%m-01")) - 1) 

# Get start date of previous month after knowing end date
start <- as.Date(format(end, "%Y-%m-01")) 

start
#> [1] "2022-02-01"
end
#> [1] "2022-02-28"

# Works in edge cases where subtracting 30 days 
# from the current datewill not give you the previous month
date <- "2022-03-01"
end <- (as.Date(format(date, "%Y-%m-01")) - 1) 
#> Error in format.default(date, "%Y-%m-01"): invalid 'trim' argument

# Get start date of previous month after knowing end date
start <- as.Date(format(end, "%Y-%m-01")) 

start 
#> [1] "2022-02-01"
end
#> [1] "2022-02-28"

^{Created on 2022-03-04 by the reprex package (v2.0.1)}

Here is a function I wrote to solve this in a more flexible way, using variable time periods (day, week, month, year) and all in base R:

calc_previous_date_range <- function(x,
                                     time_period = c("day", "week", "month", "year"),
                                     multiplier = 1,
                                     is_complete = TRUE,
                                     week_start = 1) {
  
  time_period <- match.arg(time_period)
  
  if (multiplier == 0) stop(call. = FALSE, "`multiplier` cannot equal 0")
  
  if (time_period == "day") {
    
    if (is_complete) {
      
      start <- x - multiplier
      
      end <- x - 1
      
    } else {
      
      start <- x - (multiplier - 1)
      
      end <- x
      
    }
    
  } else if (time_period == "week") {
    
    if (is_complete) {
      
      start <- cut(x - (7 * multiplier), breaks = 'week', start.on.monday = week_start) 
      start <- as.Date(start)
      
      end <- cut(x, breaks = "week", start.on.monday = week_start) 
      end <- as.Date(end)
      
      end <- end - 1
      
    } else {
      
      start <- cut(x, breaks = 'week', start.on.monday = week_start) 
      
      if (multiplier > 0) {
        start <- as.Date(start) - (7 * (multiplier - 1)) 
      }
      
      end <- x
      
    }
    
  } else if (time_period == "month") {
    
    if (is_complete) {
      
      end <- as.Date(format(x, "%Y-%m-01")) - 1
      
      start <- as.Date(format(as.Date(end), "%Y-%m-01"))
      
      if (multiplier > 1) {
        
        old_month <- as.numeric(format(start, "%m"))
        
        old_year <- as.numeric(format(start, "%Y"))
        
        # Calc new month
        new_month <- format(seq(start, length = multiplier, by = "-1 months")[multiplier], "%m")
        
        # Calc new year
        if (multiplier >= old_month) {
          
          new_year <- old_year - (1 + floor(((multiplier - old_month) / 12)))
          
        } else {
          
          new_year <- old_year
          
        }
        
        start <- as.Date(paste0(new_year, "-", new_month, "-01")) 
        
      }
      
    } else {
      
      start <- format(x, "%Y-%m-01")
      
      start <- as.Date(start)
      
      if (multiplier > 1) {
        
        old_month <- as.numeric(format(start, "%m"))
        
        old_year <- as.numeric(format(start, "%Y"))
        
        # Calc new month
        new_month <- format(seq(start, length = multiplier, by = "-1 months")[multiplier], "%m")
        
        # Calc new year
        if (multiplier >= old_month) {
          
          new_year <- old_year - (1 + floor(((multiplier - old_month) / 12)))
          
        } else {
          
          new_year <- old_year
          
        }
        
        start <- as.Date(paste0(new_year, "-", new_month, "-01")) 
        
      }
      
      end <- x
      
    }
    
  } else if (time_period == "year") {
    
    if (is_complete) {
      
      end <- as.Date(format(x, "%Y-01-01")) - 1
      
      start <- as.Date(format(as.Date(end), paste0(as.numeric(format(end, "%Y")) - (multiplier - 1), "-01-01"))) 
      
    } else {
      
      start <- format(x, "%Y-01-01") 
      
      start <- as.Date(start)
      
      if (multiplier > 1) {
        
        old_year <- as.numeric(format(as.Date(start)))
        
        start <- format(start, old_year - (multiplier - 1), "-%m-01") 
        
        start <- as.Date(start)
        
      }
      
      end <- x
      
    }
    
  }
  
  c(start, end)
  
}

Some examples:

# Last 6 days (including partial days, i.e. today)
calc_previous_date_range(Sys.Date(), "day", 6, is_complete = FALSE)
#> [1] "2022-02-27" "2022-03-04"

# Last complete 6 days 
calc_previous_date_range(Sys.Date(), "day", 6, is_complete = TRUE)
#> [1] "2022-02-26" "2022-03-03"

# Last 3 weeks (including current week)
calc_previous_date_range(Sys.Date(), "week", 3, is_complete = FALSE)
#> [1] "2022-02-14" "2022-03-04"

# Last 3 complete weeks
calc_previous_date_range(Sys.Date(), "week", 3, is_complete = TRUE)
#> [1] "2022-02-07" "2022-02-27"

# Last 3 complete weeks where week start is Sunday instead of Monday
calc_previous_date_range(Sys.Date(), "week", 3, is_complete = TRUE, week_start = 0)
#> [1] "2022-02-06" "2022-02-26"

# Last month (including current month)
calc_previous_date_range(Sys.Date(), "month", 1, is_complete = FALSE)
#> [1] "2022-03-01" "2022-03-04"

# Last complete month
calc_previous_date_range(Sys.Date(), "month", 1, is_complete = TRUE)
#> [1] "2022-02-01" "2022-02-28"

# Last 6 complete months
# Note that the year is handled properly 
calc_previous_date_range(Sys.Date(), "month", 6, is_complete = TRUE)
#> [1] "2021-09-01" "2022-02-28"

# Last year (including current year)
calc_previous_date_range(Sys.Date(), "year", 1, is_complete = FALSE)
#> [1] "2022-03-01" "2022-03-04"

# Last year (excluding current year)
calc_previous_date_range(Sys.Date(), "year", 1, is_complete = TRUE)
#> [1] "2021-01-01" "2021-12-31"

# Last 3 years (excluding current year)
calc_previous_date_range(Sys.Date(), "year", 3, is_complete = TRUE)
#> [1] "2019-01-01" "2021-12-31"