Thanks! Lots for me to learn 
This one now works fine. Not sure why I didn’t get this right yesterday
myfile="test2.csv"
dmft = dateformat"d/m/yyyy HH:MM:SS"
df = DataFrame(CSV.File(joinpath(@__DIR__,myfile)))
println(first(df,10))
using Gadfly
display(plot(df2, x="Date", y="Col3", Guide.xticks(label=false), Geom.line, Theme(grid_line_width=0mm)))
EDIT:
I think I was confused because there is a post that says the DateTime must be in String for plotting. That is not true. That led me down the rabbit hole. Here it is with plotly. All is good now.
using IterableTables
using DataFrames
using CSV
using Dates
using Plots
myfile="test2.csv"
dmft = dateformat"d/m/yyyy HH:MM:SS"
df = DataFrame(CSV.File(joinpath(@__DIR__,myfile); dateformat=dmft))
println(first(df,10))
df2 = filter(row -> row[:Date] <= Dates.DateTime("2020-10-15T00:06:00"), df)
plotly()
using StatsPlots
@df df plot(:Date, :Col3)
