Confused over contract values

Hi, I am looking at a contract that has the following lines

uint256 constant public INCREASE_RATE = 350000000000000;
uint256 constant public START_TIME = 1514228838;
uint256 constant public END_TIME =   1524251238;

I understand that the INCREASE_RATE is 0.00035eth however I am confused as to why its in the format 350000000000000 rather than 00035

I am also confused to the values 1514228838 and 1524251238 how do these translate to dates?

Thank you.