old_contents: import datetime
  import numpy as np
  
  class Epoch(datetime.datetime):
  	@property
  	def jd(self):
  		jd = (367.0 * self.year
  			 - np.floor( (7 * (self.year + np.floor( (self.month + 9) / 12.0) ) ) * 0.25 )
               + np.floor( 275 * self.month / 9.0 )
               + self.day + 1721013.5
               + ( (self.second/60.0 + self.minute ) / 60.0 + self.hour ) / 24.0)
  		return jd
  
  	@property
  	def jd2000(self):
  		return self.jd - 2451544.5
  
  	@property
  	def jd1950(self):
  		return self.jd - 2433282.5
  
  	@property
  	def mjd(self):
  		return self.jd - 2400000.5
  
  class State:
  	def __init__(self, x, y, z, vx, vy, vz, epoch=Epoch(2000,1,1,0,0,0)):
  		self.r = np.array([x, y, z])
  		self.v = np.array([vx, vy, vz])
  		self.t = epoch
new_contents: import datetime
  import numpy as np
  
  class Epoch(datetime.datetime):
  	@property
  	def jd(self):
  		jd = (367.0 * self.year
  			 - np.floor( (7 * (self.year + np.floor( (self.month + 9) / 12.0) ) ) * 0.25 )
               + np.floor( 275 * self.month / 9.0 )
               + self.day + 1721013.5
               + ( (self.second/60.0 + self.minute ) / 60.0 + self.hour ) / 24.0)
  		return jd
  
  	@property
  	def jd2000(self):
  		return self.jd - 2451544.5
  
  	@property
  	def jd1950(self):
  		return self.jd - 2433282.5
  
  	@property
  	def mjd(self):
  		return self.jd - 2400000.5
  
  class State:
  	def __init__(self, x, y, z, vx, vy, vz, epoch=Epoch(2000,1,1,0,0,0), frame="MEE2000"):
  		self.r = np.array([x, y, z])
  		self.v = np.array([vx, vy, vz])
  		self.t = epoch
subject: Prepare core.py for deletion.