Choice to fixe the data timezone or not...

Dygraphs sticks to the timezone of the machine. In certain cases, among whom most with people with whom I work, we wish to fix the timezone of the data, about are the machine, places....
We can do that using moment.js and moment-timezone.js, and a appropriate dygprahs.js with custom valueFormatter, axisLabelFormatter, and ticker.
I do quite the same things like 
http://stackoverflow.com/questions/24196183/dygraph-showing-dates-in-an-arbitrary-timezone/24196184#24196184
I think it can be very usefull.

Try this 
devtools::install_github(c("bthieurmel/dygraphs"))
mytz = "Indian/Mahe"
mytz = "UTC"

n=300
don <- data.frame(date = seq(c(ISOdate(2000,3,20)), by = "10 min", length.out = n), a = rnorm(n,100, 100), b = rnorm(n,100, 100))
attr(don[,1],"tzone") <- mytz
don <- xts(don[,-1], order.by=don[,1])

d = dygraph(don, main ="Example dygraph", ylab = "Random data", fixed.tz.data = TRUE) %>% 
  dyRangeSelector(keepMouseZoom = TRUE) %>%
  dyLegend(show = "always",labelsSeparateLines = TRUE)

d

saveWidget(d, "widget.html")
saveWidget(d, "widget2.html", selfcontained = FALSE)
I think this stuff might be better as part of the dyOptions function (the philosophy is to keep the main dygraph function as clutter-free as possible). You can pretty much use this same code there but just apply it to the "x" passed in as part of the dygraph.