require(biwavelet)
new_time <- seq(as.POSIXct('1980-01-01'),
                as.POSIXct('2010-01-01'),
                "month")
d1 <- rnorm(length(new_time))
d <- data.frame(time = new_time, dat = d1)
wt.t1 <- wt(d)
plot(wt.t1, form = '%Y')

new_time <- seq(as.POSIXct('1980-01-01'),
                as.POSIXct('2010-01-01'),
                "day")
d1 <- rnorm(length(new_time))
d <- data.frame(time = new_time, dat = d1)
wt.t1 <- wt(d)
plot(wt.t1, form = '%Y')