The calendar spread

Sell a near-dated option and buy a longer-dated one at the same strike.
You are not betting on direction. You are betting on time and on volatility — whether you meant to or not.

What it is

Two legs, same strike, two different expiries.
You sell the near one. It decays fastest, which is the income.
You buy the far one. It decays more slowly, and it is what you still own afterwards.
You pay the difference — a calendar always costs money to open.

What you are actually agreeing to

You want the stock to sit near the strike until the near option expires.
You keep the far option afterwards, and it is worth whatever it is worth then.
Your maximum loss is roughly what you paid, which is small.
Your outcome depends on implied volatility at the near expiry, not only on the price. That is the part nobody mentions.

The trade, written out

Everything above is the idea. This is the position — the lines you would actually send to a broker.

Order ticket

Leg	Action	Qty	Expiry	DTE	Strike	Delta	Price
1	Sell to open	-1	1 Oct 26	30	100 Put	+0.47 (47Δ)	$2.69
2	Buy to open	+1	31 Oct 26	60	100 Put	-0.45 (45Δ)	$3.71
Net	Debit	1 position	1 Oct 26	30	—	+0.01	$1.02

BUY +1 CALENDAR XYZ 1 OCT 26/31 OCT 26 100/100 PUT @ 1.02 DEBIT

Reading it back

Same strike on both legs. Only the dates differ.
The near leg is sold, the far leg is bought.
The ticket shows a debit. There is no version of this that pays you to open it.
The DTE column is the whole structure — look there rather than at the strikes.

The argument

Bull

makes the claim

The near option loses value faster than the far one, every single day. I am buying that difference for a small, defined amount. If the stock sits still I am paid for its stillness and I still own the long option afterwards.

Bear

doubts it

You have bought something whose value at the moment of truth depends on a number nobody can forecast — the implied volatility of the far leg on that day. Get the price right, get the volatility wrong, and you still lose. That is two forecasts to pay for one.

Ferret

settles it

Then a test of this cannot use a fixed volatility, and most published calendar backtests do exactly that. Until we can price the far leg with its own implied volatility on the day, we should not publish a calendar result at all.

The shape of it

The calendar spread on XYZ at $100 · 25% volatility · 4% rate · 30 days. Priced from the model, not written by hand.

	At expiry
Debit paid	$102
Maximum profit	$168
Maximum loss	$-134
Breakevens	$96.03, $104.93

A hill centred on the strike — the opposite shape from a credit spread.
The best outcome is the stock finishing exactly at the strike when the near option expires.
Maximum loss is close to what you paid, in either direction.
The shape at the near expiry is a model price, not intrinsic value, because the far leg is still alive. That is stated on the chart and it matters.

Where you actually enter

The chart above is the shape at expiry. It puts the bend right next to the money, which makes the trade look like it is already on the edge. It is not — here is the day you open it.

The same structure set up at 50Δ · 30 days · credit $102. The shaded band is the room between the stock and the strike you sold.

The same price, two different days

	On day one	At expiry
Stock at $100 (the strike you sold)	$0	$168
Stock unchanged at $100	$0	$168

You enter at the top of the hill — but a very flat hill.
The position is worth almost nothing to you on day one. The whole gain comes from time passing.
Everything about a calendar happens at the end, which makes an early exit rule almost meaningless on it.
The two lines are closer together here than on any other structure, which is another way of saying the same thing.

Different ways to set it up

The dial that matters is where the near expiry sits, and the gap between the two legs. The panels below hold the gap at thirty days and move the near leg.

Same delta, four tenors

Days	Short strike	Away from spot	Credit	Max loss	Risk : reward
7	100	+0.0%	$163	$-196	—
14	100	+0.0%	$134	$-167	—
30	100	+0.0%	$102	$-134	—
60	100	+0.0%	$74	$-107	—

A short near leg costs the most and works the fastest. There is very little value in a seven-day option, so you pay nearly the full price of the far one.
A longer near leg costs far less, because the two options are closer in value.
The trade-off is time. The cheap version takes months to resolve; the expensive one is over in a week.

A calendar is priced by the difference between two dates. Which two you choose is the entire specification.

What the Greeks are doing

Four questions about the same position, and a fifth that barely applies here.
Every structure answers them differently, which is why this site never writes a general page about the Greeks.

Days left	Delta	Gamma	Theta / day	Vega	Rho
30	+1.3	-1.64	$+1.40	$+4.67	$-4.01
14	+1.7	-3.56	$+3.05	$+5.98	$-4.04
5	+2.2	-8.49	$+7.27	$+7.64	$-4.05

The position at entry — stock $100 · 25% volatility. Per contract, from the model.

Delta — which way you need the stock to go

Near zero at the strike, and it turns against you in both directions.
You want the stock to do nothing, which is a rare thing to actually want.

Theta — what time does to you

Positive, and that is the entire trade.
The near leg decays faster than the far leg. You own that difference.

Vega — what a change in fear does to you

Long volatility — the only structure on this shelf that is.
The far leg has more vega than the near one, so rising implied volatility helps you.
That is why this is a volatility trade. The price chart is only half the story.

Gamma — how fast your delta turns against you

Negative near the strike, from the short leg.
It is smaller than a naked short option’s, because the far leg is buying some of it back.

Rho — what a change in interest rates does to you

Larger than on a single-expiry structure, because the two legs sit at different dates.
Still small enough for one row.

Theta and gamma are one thing

This is the part that decides whether the strategy works, and it is almost never put plainly.

You cannot be paid theta without being short gamma. They are not two features of the trade. They are the rent and the risk on one lease.

The same position, three points in its life

Nothing about the position changes.
The stock sits still at $100 throughout.
Only the days left move.

Days left	Delta	Gamma	Theta / day	Vega	Rho
30	+1.3	-1.64	$+1.40	$+4.67	$-4.01
14	+1.7	-3.56	$+3.05	$+5.98	$-4.04
5	+2.2	-8.49	$+7.27	$+7.64	$-4.05

Now move the stock to $96.00

Same three dates, same calendar.
Now with the stock a few dollars off the strike — where the hill starts to fall away.

Days left	Delta	Gamma	Theta / day	Vega	Rho
30	+7.4	-1.21	$+0.89	$+5.15	$-4.80
14	+13.7	-1.80	$+1.29	$+6.87	$-5.07
5	+24.4	-0.74	$+0.34	$+9.00	$-5.40

Gamma goes from -1.21 to -0.74.
Theta goes from $+0.89 a day to $+0.34.
Both climb, and neither is available without the other.
Delta now moves roughly 1 times as far for every dollar the stock travels.

Which is what DTE actually sets

On a calendar, DTE is not one dial — it is two.
The near leg sets how fast you are paid. The gap sets what you still own afterwards.
Shortening the near leg raises both the income and the sensitivity, the same way it does everywhere else.
The difference is that here you are long vega, so a volatility spike is help rather than harm.

The trap

The trap is that it looks like a trade about price.

A calendar is a volatility trade wearing a direction trade’s clothes.

The chart shows a hill over the strike, so it reads as “I want the stock here”.
But the far leg has to be sold or valued at the near expiry, and what it is worth then depends on implied volatility that day.
Price right, volatility down, and the trade still loses.
No other structure on this shelf has that property.

Why it matters, and what it means for testing

A backtest that assumes one fixed volatility cannot test a calendar honestly.
It will produce a number, and the number will be wrong in a direction nobody can predict.
Until we can price the far leg with its own implied volatility, this site will not publish a calendar result.
That limit is written down in our own engine roadmap rather than discovered later.

How this shows up in our tests — pending. No result has been published on this structure yet.