r - POSIXlt list problem with which funciton in R

Question

I have a problem with a list of type Large POSIXlt in my project. The list is called time and has 11315 entries. When I make the command:

$ which(time=="1985-01-01")

R return the good index 1 but for the entries beyond 91 with the command

$ which(time=="1985-04-01")

it returns integer(0) instead of 91.

Since the data have been downloaded for a project I don't made them but I tried to make my own list of POSIXlt and there is the same problem for all the indexes.

If someone can help me it will be very heroic.

PS: here are the information about the version of R and my computer (I'm on ubuntu 18.04)

platform x86_64-pc-linux-gnu
arch x86_64
os linux-gnu
system x86_64, linux-gnu
status
major 3
minor 4.4
year 2018
month 03
day 15
svn rev 74408
language R
version.string R version 3.4.4 (2018-03-15) nickname Someone to Lean On

标签： r