text: #faster
  import datetime as dt
  ages = pd.Series()
  tweets_df["createdAt"] = pd.to_datetime(tweets_df["createdAt"])
  for j in range(len(users_df["id"]):   
      try:
          k = float(users_df["id"][j])
          x = tweets_df["createdAt"].where(tweets_df["userID"]==k).max()
          y = tweets_df["createdAt"].where(tweets_df["userID"]==k).min()
          a = x-y
          a = a.total_seconds()
          ages = ages.append(to_append=pd.Series([a],index=[k]))        
      except: 
          pass
  
  