Call Calendar Spread

What you will learn

• Uses more than one expiration

What it is and when to use it

A calendar spread — or horizontal spread — exploits the fact that the near option loses time value far faster than the far one. By selling the 30 days and buying the 60, you collect that difference in pace: the short melts at $18.90 a day and the long at only $14.00, and those $4.88 of difference are the profit per day if price does not move.

The Greek combination is unusual and it is what makes it useful: positive theta (+$4.88/day) and positive vega too (+$26.98). Almost every positive-theta position is short volatility; this one is not. It profits if time passes AND it profits if implied volatility rises, which makes it the preferred structure for expressing "this is not moving now, but it will move later".

You use it with implied volatility low — the opposite of the condor or the butterfly — because a long-vega position wants implied volatility to rise. And you use it around a specific level, because the profit concentrates in a narrow peak around the strike, just as in a butterfly.

How it is built

• Sell 1 call at the strike where you expect price to be, with a near expiry (30 days is usual).
• Buy 1 call at the SAME strike with a far expiry (60 days, or twice the first).
• The net debit is the difference between the two premiums and is roughly the maximum loss.
• It can be built with puts in the same way: the profile is practically identical.

The same strike is what distinguishes it from a diagonal. If the strikes differ, the structure picks up a directional bias on top of the time one, and that changes the analysis completely.

A full worked example

SPY at 580.00, strike 580 on both legs, selling the 30-day expiry and buying the 60-day.

Net debit = 4.82 × 100 = $482.

Note that twice the time does not cost twice the premium: 15.48 against 10.66, barely 45% more. Time value grows with the square root of time, not with time, and that fact is literally the engine of this strategy.

Maximum profit, maximum loss and break-evens

This is the most important practical difference from the rest of these pages: in a calendar, the expiry numbers depend on the FUTURE implied volatility of the long leg, which is not known today. That is why payoff calculators draw a curve and not a broken line.

• Maximum loss ≈ debit = $482. It is approached if price moves far from the strike in either direction.
• Maximum profit: there is no closed formula. It depends on what the 60-day call is worth on the day the 30-day expires, and with price at 580 that value is around 10.66 points against a net cost of 4.82.
• Break-evens: not fixed either. They are computed on the long leg’s value at the short leg’s expiry, not on the strikes.
• Optimum = price exactly at 580 on the day the short call expires.

That dependence on future implied volatility is what makes a calendar need a real tool to value it. With the Greeks and a model you can estimate the result; with the usual four rules of thumb, you cannot.

The position Greeks

Positive theta with positive vega is a rare combination and it is the whole argument for the strategy. A condor profits from time and loses if volatility rises; a calendar profits from both, and that is why it is opened with implied volatility low.

Management: when to close, when to roll

Close before the short leg expires

Letting the 30-day call expire with price near 580 is asking for an assignment that leaves you short 100 shares covered by a 60-day call. It works, but it is a different position with different margin requirements.

Rolling the short leg

The classic management: when the 30-day expires, sell another at the same strike in the next cycle. Each roll collects new premium and lowers the net cost of the long leg, which is how a calendar turns into an income position.

If price moves away

The position loses value slowly, because the negative gamma is small. That buys time: moving the whole calendar to the new level is viable and usually cheap.

If implied volatility jumps

Positive vega of +$26.98 per point can hand you a fast profit without price having done anything. That is a good moment to close: high implied volatility is what paid you, and it usually comes back down.

Common mistakes

Opening it with implied volatility high

It is the mirror image of the condor mistake. A calendar is long vega, so opening it with implied volatility at highs means mean reversion works against you from day one.

Expiries too far apart

Selling 30 days and buying 180 looks like it maximises the decay difference, and what it actually does is blow up the cost and the volatility exposure. The usual ratio is one to two.

Ignoring the dividend

A dividend between the two expiries affects each leg differently and shifts the optimum. In SPY, with four distributions a year, there is almost always one in between.

Expecting a straight-line payoff

A calendar’s diagram is a curve that depends on future implied volatility, not a broken line. Working it out "by hand" from the strikes gives a number that means nothing.