Function greg2abs

greg2abs(date: Date): number
Converts Gregorian date to absolute R.D. (Rata Die) days
Parameters
- date: Date
  Gregorian date
Returns number
Example
```
greg2abs(new Date(2008, 10, 13)); // 733359 (13 November 2008)
greg2abs(new Date(2005, 3, 2)); // 732038 (2 April 2005)
```
- Defined in greg.ts:111