merging 2 frames while keeping all the entries from the "reference" frame

Hello!
I have my data frame "mydata" (below) and data frame "reference" -
that contains all the dates I would like to be present in the final
data frame.
I am trying to merge them so that the the result data frame contains
all 8 dates in both subgroups (i.e., Group1 should have 8 rows and
Group2 too). But when I merge it it's not coming out this way. Any
hint would be greatly appreciated!
Dimitri

mydata<-data.frame(mydate=rep(seq(as.Date("2008-12-29"), length = 8,
by = "week"),2),
group=c(rep("Group1",8),rep("Group2",8)),values=rnorm(16,1,1))
(reference);(mydata)
set.seed(1234)
out<-sample(1:16,5,replace=F)
mydata<-mydata[-out,]; dim(mydata)
(mydata)

# "reference" contains the dates I want to be present in the final data frame:
reference<-data.frame(mydate=seq(as.Date("2008-12-29"), length = 8, by
= "week"))

# Merging:
new.data<-merge(mydata,reference,by="mydate",all.x=T,all.y=T)
new.data<-new.data[order(new.data$group,new.data$mydate),]
(new.data)
# my new.data contains only 7 rows in Group 1 and 4 rows in Group 2

library(zoo)
z <- merge(read.zoo(mydata, split = 2), zoo(, reference[[1]]), all = c(FALSE, TRUE))
z