R Shiny DT - edit values in table with reactive

If you don't show the row names in your DT then you should add 1 to info$col to get the correct column i.e., j = info$col + 1.

I am not sure if I understand you correctly, but maybe this solution might help you a bit. I changed your reactive into a reactiveValues object and I removed the replaceData line.

library(shiny)
library(DT)
shinyApp(
  ui = fluidPage(
    DTOutput('x1'),
    verbatimTextOutput("print")
  ),
  server = function(input, output, session) {
    x = reactiveValues(df = NULL)

    observe({
      df <- iris
      df$Date = Sys.time() + seq_len(nrow(df))
      x$df <- df
    })

    output$x1 = renderDT(x$df, selection = 'none', editable = TRUE)

    proxy = dataTableProxy('x1')

    observeEvent(input$x1_cell_edit, {
      info = input$x1_cell_edit
      str(info)
      i = info$row
      j = info$col
      v = info$value

      # problem starts here
      x$df[i, j] <- isolate(DT::coerceValue(v, x$df[i, j]))
    })

    output$print <- renderPrint({
      x$df
    })
  }
)