How many days are there in 400 years of the current western (Gregorian) calendar?

Player #4269245, I did as you said 365x400+40 which equalled 146100 Which was wrong For some reason you have take off 3 to give 146097 Dont know why? Anyone?

Player #4269245, yes Sheldon lol

So need to calculate 365x400 and also slot in the leap years in less than 10 seconds? 🤔