[R] Date format

[Medic]

I took a SAMPLE CODE (for Connected scatterplot) from the R gallery
and applied to MY DATA, but got:
"Error in as.Date.numeric(mydata$date) : 'origin' must be supplied".
P.S. I can not understand ?as.Date()

SAMPLE CODE
library(ggplot2)
library(dplyr)
library(hrbrthemes)
data <- read.table("https://raw.githubusercontent.com/holtzy/data_to_viz/master/Example_dataset/3_TwoNumOrdered.csv",
header=T)

str(data)
'data.frame': 1822 obs. of  2 variables:
 $ date : chr  "2013-04-28" "2013-04-29" "2013-04-30" "2013-05-01" ...
 $ value: num  136 147 147 140 126 ...

data$date <- as.Date(data$date)

# Plot
data %>%
  tail(10) %>%
  ggplot( aes(x=date, y=value)) +
    geom_line( color="grey") +
    geom_point(shape=21, color="black", fill="#69b3a2", size=6) +
    theme_ipsum() +
    ggtitle("Evolution of bitcoin price")


MY DATA
mydata <- read.table("E:/mydata.csv", header=TRUE, sep=";", dec=",")

str(mydata)
'data.frame': 7 obs. of  2 variables:
 $ date : chr  "01.01.2000" "02.01.2000" "03.01.2000" "04.01.2000" ...
 $ value: int  11 12 13 14 15 16 17

mydata$date <- as.Date(mydata$date)
Error in as.Date.numeric(mydata$date) : 'origin' must be supplied