Does this code "delay(86400000);" delay 1 day?
I tried this for a watering system but it seems doesn't work.
Please advice. Thanks.
Time values should be stored and manipulated as unsigned long. To ensure that your literal numbers are treated as the correct type, use the UL suffix:
delay(86400000UL);
If that doesn't correct the problem, you will need to explain exactly what "doesn't work" means.
You do realise that during the delay your Arduino will not be able to do anything useful.
Thanks, it works!
Did it take long to test ? 
About 24 hours I'd say.