Why do I get "Error in rbind.zoo(...) : indexes overlap" when merging two zoo objects?

Question

I have two seemingly identical zoo objects created by the same commands from csv files for different time periods. I try to combine them into one long zoo but I'm failing with "indexes overlap" error. ('merge' 'c' or 'rbind' all produce variants of the same error text.) As far as I can see there are no duplicates and the time periods do not overlap. What am I doing wrong? Am using R version 3.0.1 on Windows 7 64bit if that makes a difference.

> colnames(z2)
[1] "Amb"  "HWS"  "Diff"
> colnames(t.tmp)
[1] "Amb"  "HWS"  "Diff"

> max(index(z2))
[1] "2012-12-06 02:17:45 GMT"
> min(index(t.tmp))
[1] "2012-12-06 03:43:45 GMT"
> anyDuplicated(c(index(z2),index(t.tmp)))
[1] 0


> c(z2,t.tmp)
Error in rbind.zoo(...) : indexes overlap
> 

UPDATE: In trying to make a reproducible case I've concluded this is an implementation error due to the large number of rows I'm dealing with: it fails if the final result is more than 311434 rows long.

> nrow(c(z2,head(t.tmp,n=101958)))
Error in rbind.zoo(...) : indexes overlap
> nrow(c(z2,head(t.tmp,n=101957)))
[1] 311434
# but row 101958 inserts fine on its own so its not a data problem.
> nrow(c(z2,tail(head(t.tmp,n=101958),n=2)))
[1] 209479

I'm sorry but I dont have the R scripting skills to produce a zoo of the critical length, hopefully someone might be able to help me out..

UPDATE 2- Responding to Jason's suggestion.. : The problem is in the MATCH but my R skills arent sufficient to know how to interpret it- does it mean MATCH finds a duplicate value in x.t whereas anyDuplicated does not?

> x.t <- c(index(z2),index(t.tmp));
> length(x.t)
[1] 520713
> ix <- ORDER (x.t)
> length(ix)
[1] 520713
> x.t <- x.t[ix]
> length(ix)
[1] 520713
> length(x.t)
[1] 520713
> tx <- table(MATCH(x.t,x.t))
> max(tx)
[1] 2
> tx[which(tx==2)]
 311371 311373 311378 311383 311384 311386 311389 311392 311400 311401 
      2      2      2      2      2      2      2      2      2      2 
 > anyDuplicated(x.t)
 [1] 0

Answer 1

After all the testing and head scratching it seems that the problem I'm having is timezone related. Setting the environment to the same time zone as the original data makes it work just fine.

Sys.setenv(TZ="GMT")
> z3<-rbind(z2,t.tmp)
> nrow(z3)
[1] 520713

Thanks to how to guard against accidental time zone conversion for the inspiration to look in that direction.