;+
;NAME:
function timeinterval,a,b
;KEYWORDS:	Yohkoh data analysis, Yohkoh Operation
;PURPOSE:
;	calculate time interval (sec) between two time structures.
;CALLING SEQUENCE:
;       sec=timeinterval(srctime,starttime)
;RETURN:
;	time (second) float array.
;INPUTS:
;	a:	time structure
;	b:	one dimensional time structure
;HISTORY:
;	Ver 1.0 96-10-25	Created by TY
;-
	aday=gt_day(a)
	asec=gt_time(a)*0.001
	if n_elements(b) ne 1 then message,/trace,'second parameter should be one dimensional structure.`
	bday=gt_day(b)
	bsec=gt_time(b)*0.001
	dday=aday-bday
	dsec=(dday*86400.)+asec-bsec
	return,dsec
end