Raspberry Pi clock on LCD screen

I think I have found an effective solution to change the display of a message at different times, but I'm sure it's very bad coding! x)

 #!/usr/bin/python

 import time
 from time import sleep, strftime, mktime
 from datetime import datetime
 import Adafruit_CharLCD as LCD

 # Initialize the LCD using the pins
 lcd = LCD.Adafruit_CharLCDPlate()

 # Horloge
 dti = mktime(datetime.now().timetuple())
 day = "06:00"
 day_screen = "07:00"    
 night = "19:50"
 night_screen = "23:50"
 hour = "%H:%M"

 # Couleur
 lcd.set_color(0.0, 1.0, 1.0)

 # Affichage
 while True:
     ndti = mktime(datetime.now().timetuple())

     if "%night" < "%hour" < "%day"
          "%mess" = "Bonsoir :)"
     else: "%day" > "%hour" < "%night"
          "%mess" = "Bonjour :)"

     if "%night_screen" < "%hour" < "%day_screen"
           enable_display()
     else: "%day_screen" > "%hour" < "%night_screen"
           enable_display()

     if dti < ndti:
          dti = ndti
          lcd.clear()
          lcd.message('   %mess\n')
          lcd.message(datetime.now().strftime('%d %b %H:%M:%S'))
          sleep(0.95)
     else:
          sleep(0.01)

I would appreciate any advice to help me correct my mistakes, thank you :)