There is one thing that puzzles me. I set up the spread---buying 1 APR ATM call and selling 1 JUN ATM call. The spread does appear as positive numbers. For instance, the recent bid/ask was 15/17. To place this spread, one has to sell it. So, I sell it for 16. Now, suppose the VIX drops 10% and the ES moves up 50 points (about 5%). What will the bid/ask look like? Having done credit spreads and only realizing the credit received as the max profit, I cannot envision what the reverse call calendar spread's bid/ask will look like. If my understanding is correct, this spread should turn negative when I go to close it (buy it back). If this is true, my broker (IB) has told me that GLOBEX doesn't accept negative bids. So, how would I exit this spread? Second, I am having a hard time envisioning the near-money call far outperforming and covering the loss from the far-money call.