New seeded lawn, sprinkle how long?

I have just had my dead front lawn re seeded.. I have been told to water it twice a day. Now I know its how long is a piece of string. But as a rule of thumb, how long should I leave the sprinkler on for each session?
TIA

 

The best way is to keep the soil damp and not saturate the area constantly. Hopefully the weather cools down a bit so it’s not so hot. This hot weather just bakes the ground so water evaporation is at very high levels.