Swisseph routine to calculate VoC. Pardon me for being lazy for not copypastaing the functions from chronoslnx that it's using in here

predict_voc.py

from chronoslnxlib.core import *

def predict_voc(cur_date):
	cycles = date_to_moon_cycles(cur_date)
	moon_pos = swisseph.calc_ut(datetime_to_julian(cur_date), swisseph.MOON)[0]
	closest_sign = (( moon_pos // 30 ) + 1) * 30
	lower_sign = ( moon_pos // 30 ) * 30
	#print(moon_pos, closest_sign)
	lower_cycles = cycles+(angle_sub(lower_sign, moon_pos)/360)
	cycles += (closest_sign - moon_pos) / 360
	diff = float('inf')
	#print(cycles)
	while abs(diff) >= 1E-8:
		closest_sign_estimate = swisseph.calc_ut(moon_cycles_to_jul(cycles), swisseph.MOON)[0]
		#print(moon_pos, closest_sign_estimate, cycles)
		diff = angle_sub(closest_sign, closest_sign_estimate)
		cycles += (diff / 360)
	#
	diff = float('inf')
	while abs(diff) >= 1E-8:
		closest_sign_estimate2 = swisseph.calc_ut(moon_cycles_to_jul(lower_cycles), swisseph.MOON)[0]
		diff = angle_sub(lower_sign, closest_sign_estimate2)
		lower_cycles += (diff / 360)
	voc_cycles = cycles
	#voc_cycles -= (1 / 36000)
	has_aspects = False
	#
	other_planets = [swisseph.SUN, swisseph.MERCURY, swisseph.VENUS, 
	                 swisseph.MARS, swisseph.JUPITER, swisseph.SATURN,
	                 swisseph.NEPTUNE, swisseph.PLUTO]
	#
	while (not has_aspects) and (voc_cycles > lower_cycles):
		voc_cycles -= (1 / 36000)
		julified = moon_cycles_to_jul(voc_cycles)
		#print(revjul_to_datetime(swisseph.revjul(julified)))
		moon_pos = swisseph.calc_ut(julified, swisseph.MOON)[0]
		#
		for i,planet in enumerate(other_planets):
			other_angle = swisseph.calc_ut(julified, planet)[0]
			for angle in (0, 60, 90, 120, 180):
				#print(moon_pos, angle, swisseph.get_planet_name(planet), other_angle)
				angle_gap = abs(angle_sub(moon_pos, other_angle))
				#print("angle gap:", angle_gap)
				#print("how far:", angle_sub(angle, angle_gap))
				if abs(angle_sub(angle, angle_gap)) <= 5E-3:
					print("Found start of VOC with", i, "@", angle, angle_gap)
					has_aspects = True
					break
		#print("---")
		#
		#print(lower_sign, moon_pos, closest_sign)
		#print( (not has_aspects),	(voc_cycles > lower_cycles) )
	else:
		if not has_aspects:
			print("Couldn't find VOC")
	return revjul_to_datetime(swisseph.revjul(moon_cycles_to_jul(voc_cycles))), moon_pos, \
	       revjul_to_datetime(swisseph.revjul(moon_cycles_to_jul(cycles))), closest_sign_estimate, closest_sign_estimate2