dateInput save as NULL

saveNullDate

library(shiny)

ui <- shinyUI(
  fluidPage(
    dateInput(inputId = "date",
              label = "Signature Date",
              value = ''),
    actionButton(inputId = "save_signature",
                 label = "Print Signature"),
    verbatimTextOutput("date_value"),
    verbatimTextOutput("signature")
  )
)

server <- shinyServer(function(input, output, session){
  output$user_name <- renderText({ input$user_name })
  output$date_value <- renderText({ input$date })
  
  sign_date <- eventReactive(input$save_signature,
                             {
                              req(input$date)
                              input$date
                             })
  
  output$signature <- renderText({ sign_date() })

})

shinyApp(ui = ui, server = server)