Funny, It all depends on the level of precision.
A person might say that there are 365 days in a year but they would be wrong 1 in 4 years as a leap year has 366 days.
As for dino and human ... if my time window was a billion years ... then yes they would have lived together.
And as for the percent of water, does the precision need to take into account only oceans and seas, or do I also need to account for ice, snow and temperate surface water?
The answer you're looking for is 365.24 days, which explains why we have a leap year every four years. Notice, however, that the fraction is just shy of a quarter, so that every 400 years we have a non-leapt leap year: i.e. the year 2400 will not be a leap year. Of course, if you remember all the way back to eight years ago, you should recall that 2000 was indeed a leap year, what gives? What gives is that every exception has it's own exception. The three rules for leap years can be summarized as follows:
1: if a year is divisible by 4 it is a leap year
2: unless it is also divisible by 400, in which case it isn't
3: unless it is also divisible by 2000, in which case it is.
What could be simpler? Well what could be simpler is just to say that the earth revolves around the sun once ever solar year, which is by definition the time it takes for the earth to revolve around the sun. Expressed in terms of days this is of course an irrational number, necessitating the whole leap year business.