Some people bath in the morning after get up. Some people bath in the evening after ending their daily work. It depends on the profession and health. Therefore it is not practical to recommend a time to bath.
When you bath cool water, blood vessels in upper skin will shrink and more blood goes to deep areas. But when bath warm water, blood vessels in upper skin will be dilated and more blood goes to upper skin area than deeper.
As a scientific experiment of Common Welth University of Virgenia, they prove that depression will be reduced when bath cool water. It is better to skin and hair to bath cool water than warm. In 1993 an investigation of English proves that, high immunity gains even against viruses when bathing cool water every day. It assumes that this is as a result of increasing chemical metabolism inside the body.
Scientific investigation reports that testosteron density increase in blood when bathing cool water. If you are a male it increases the production of sperms in your testis. Production of sperms needed a lower temperature. That's why the testis have come out of the body.
Concerning all these we are recomond you to bath atleast once a day.