No, you should never apply Melacare in the daytime, as it can react very badly to sunlight, causing damage to your skin!
Melacare cream should ONLY be applied as directed by the doctor who prescribed it, and please note that I am NOT a doctor, I am just here to give you advice.
Melacare cream should never be used in the daytime as it reacts severely to the sun as it contains hydroquinone. Actually, even when you have washed it off in the morning, it is advisable to use sun screen if going out in the sun as skin can literally turn black.
Melacare cream should be applied at bedtime in a thin layer and rubbed in gently.
I have heard great things about this cream and also not so good things, I think it is like anything, it suits some people but not others. Just take care and read the accompanying leaflet and you should be fine if you use it at night as directed.
I found another answer on here which may be of some use to you, which you can read here