如何在shinyapp中捕获两个inputDate()并计算天数？

dateInput("start_date", "选择起始日期：", value = Sys.Date())
dateInput("end_date", "选择结束日期：", value = Sys.Date())

observeEvent(input$start_date, {
  start_date <- as.Date(input$start_date)
  end_date <- as.Date(input$end_date)
  days <- difftime(end_date, start_date, units = "days")
  output$days <- renderText(paste("两个日期之间的天数差为：", days, "天"))
})

textOutput("days")

library(shiny)

ui <- fluidPage(
  dateInput("start_date", "选择起始日期：", value = Sys.Date()),
  dateInput("end_date", "选择结束日期：", value = Sys.Date()),
  textOutput("days")
)

server <- function(input, output) {
  observeEvent(input$start_date, {
    start_date <- as.Date(input$start_date)
    end_date <- as.Date(input$end_date)
    days <- difftime(end_date, start_date, units = "days")
    output$days <- renderText(paste("两个日期之间的天数差为：", days, "天"))
  })
}

shinyApp(ui, server)