Julian Days can also be used to tell time; the time of day is expressed as a fraction of a full day, with 12:00 noon (not midnight) as the zero point. So, 3:00 pm on 1 Jan 1970 is JD 2440588.125 (since 3:00 pm is 3 hours since noon, and 3/ 24 = 0.125 day). Note that the Julian Day is always determined from Universal Time, not Local Time.
Tamén se poden empregar os días xulianos para expresar a hora; a hora do día exprésase como fracción dun día completo, sendo as 12. 00 do mediodía (non da medianoite) o punto cero. Polo tanto, as 3. 00 das tarde do 1 de xaneiro de 1970 son DX 2440588. 125 (dado que as 3. 00 da tarde son tres horas despois do mediodía e 3/ 24 = 0, 125 días). Observa que o día xuliano se determina sempre a partir da Hora universal e non da hora local.