SLA_CLDJ - Calendar to MJD

ACTION:

Gregorian Calendar to Modified Julian Date.

CALL:

CALL sla_CLDJ (IY, IM, ID, DJM, J)

GIVEN:

IY,IM,ID

I

year, month, day in Gregorian calendar

RETURNED:

DJM	D	modified Julian Date (JD$-$2400000.5) for $0^{\rm h}$
J	I	status:
		0 = OK
		1 = bad year
		2 = bad month
		3 = bad day

NOTES:

1. When an invalid year or month is supplied (status J = 1 or 2) the MJD is not computed. When an invalid day is supplied (status J = 3) the MJD is computed.
2. The year must be $-$4699 (i.e. 4700BC) or later. For year $n$BC use IY = $-(n-1)$.
3. An alternative to the present routine is sla_CALDJ, which accepts a year with the century missing.

REFERENCE:

The algorithm is adapted from Hatcher, Q.Jl.R.astr.Soc. (1984) 25, 53-55.