A date and time algorithm defined by ECMAScript.
|Property/method value type:||Number primitive|
A date number is identified by an integer in the range 1 through 31, inclusive. The specific range depends on the month being considered and whether a leap year is in force.
ECMA 262 edition 2 - section - 18.104.22.168
ECMA 262 edition 3 - section - 22.214.171.124