"It is already midnight and they are still running."
Translation:כבר חצות והם עדיין רצים.
As it has already asked and answered, no, you can't say that in Hebrew. English often times uses "dummy subject" - it, while Hebrew has no need for it. The same things happens with the following phrases, where you have "it" in English, but you don't put זה in Hebrew: "it seems that..." נראה ש, "it is important (for me) that..." חשוב לי ש, "it is raining" יורד גשם, "it is hot today" חם היום, "it is late already" כבר מאוחר, "it is midnight already" כבר חצות, "it is six o'clock" השעה שש and so on.