How to Order ggplot2 x-axis dates chronologically when in mm-yyyy format?

Question

I'm designing an R program to output different graphs of any csv file input. I am using Rstudio Shiny and ggplot2 to develop the program.

My problem involves ordering dates chronologically rather than alphabetically (which is the default apparently). Let's use this code as an example (my code is a bit different, but this is code from someone who helped me earlier):

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server.R

library(shiny)
library(datasets)
library(ggplot2)

X <- read.csv(file.choose())
# Define server logic required to summarize and view the selected dataset
shinyServer(function(input, output) {
  output$opt.x <- renderUI({
    selectInput("xcolumn", "X column to Plot",
                names(Y()) 
                )
  })

  output$opt.y <- renderUI({
    selectInput("ycolumn", "Y Column",
                names(Y()))
  })

  # Generate a summary of the dataset
  output$summary <- renderPrint({
    dataset <- X
    summary(dataset)
  })

  # Show the first "n" observations
  output$view <- renderTable({
    head(X, n = input$obs)
  })

  createPlot <- function(df, colx, coly) {
    p <- ggplot(data=df, aes(x=df[,colx],y=df[,coly]), environment = environment()) #+ geom_line(aes(x=df[,colx],y=df[,coly], group=colx))
    p <- p + geom_line(aes(group=colx)) 
    p <- p + xlab(names(df)[colx]) + ylab(names(df)[coly]) 
  }

  Y <- reactive({
    X
      })



  # create a basic plot
  output$plotBasic <- reactivePlot(function() {
    df <- Y()
    print(createPlot(df, colx=input$xcolumn, coly=input$ycolumn))

  })
})

ui.R

library(shiny)

# Define UI for dataset viewer application
shinyUI(pageWithSidebar(
  # Application title
  headerPanel("My app!"),

  # Sidebar with controls to select a dataset and specify the number
  # of observations to view
  sidebarPanel(
    numericInput("obs", "Number of observations to view:", 13),
    uiOutput("opt.x"), #dynamic UI
    uiOutput("opt.y") #value comes from Server.R    
    ),

  # Show a summary of the dataset and an HTML table with the requested
  # number of observations
  mainPanel(
    tabsetPanel(
      tabPanel("Table", tableOutput("view")),
      tabPanel("BasicGraph", plotOutput("plotBasic"))
    )
  )
))

This can be taken care of easily with factor or as.Date functions if you started with a list that you knew of, but here I am taking in input (can assume the format is mm-yyyy) and I do not know how to set the column of x variable data to a variable. This is because the user can choose any column in the imported data as the X column.