Group dates based on specific number of days in R

I have a DateTime series (see below as an example). I have to assign groups to these dates based on 8 days intervals. Basically, the group should be assigned as per the following rules (for any given year): - Group 1: (Jan 1 - Jan 8); Group 2: (Jan 9 - Jan 16); and so on. So, basically, there will be 46 groups (~(365 or 366)/8) in total in a year. The last group in a ye开发者_JAVA百科ar will have only either 5 days or 6 days (365 or 366 - 45*8). What is a convenient way to approach this?

    x <- as.POSIXct("2021-12-31") + as.difftime(c(1:10,50,100,350,364,470), units="days")

Using cut with a sequence of 8 day blocks, compared to the Julian days extracted from each date object.

Example data:

x <- as.POSIXct("2021-12-31") + as.difftime(c(1:10,50,100,350,364,470), units="days")

Cut and review results:

grp <- cut(as.integer(format(x, "%j")), breaks=c(seq(0,366,8), 366))
data.frame(x, grp)

#            x       grp
#1  2022-01-01     (0,8]
#2  2022-01-02     (0,8]
#3  2022-01-03     (0,8]
#4  2022-01-04     (0,8]
#5  2022-01-05     (0,8]
#6  2022-01-06     (0,8]
#7  2022-01-07     (0,8]
#8  2022-01-08     (0,8]
#9  2022-01-09    (8,16]
#10 2022-01-10    (8,16]
#11 2022-02-19   (48,56]
#12 2022-04-10  (96,104]
#13 2022-12-16 (344,352]
#14 2022-12-30 (360,366]
#15 2023-04-15 (104,112]