Calendar Spread Advanced

Buying a single option means you fight time decay (theta) every day - your option loses value even if you're right about direction. Calendar spreads use time decay in your favor because you sell a faster-decaying near-term option. You also reduce cost basis significantly. The trade-off is limited profit potential and the requirement for price to stay near your strike rather than moving significantly in your favor.

Yes, calendar spreads work well with weekly options in the UK, because FTSE 100 index options have both weekly and monthly expiries. You can sell a current-week option and buy a next-week or monthly option. Weekly calendars capture rapid theta decay in the front leg. However, the shorter timeframe means less room for error - price must stay near the strike within 4-5 days. Start with weekly-to-monthly calendars for more forgiveness before trying weekly-to-weekly. (FTSE 250 and single-stock options are monthly only, so weekly calendars are an FTSE 100 feature.)

If the front month expires out-of-the-money, it becomes worthless and you're left with just the long back month option. FTSE 100 index options are European-style and cash-settled, so there is no early assignment - but if the front is in-the-money at expiry it settles in cash and you lose the time-spread structure. Single-stock options are American-style and physically settled, so a short ITM leg can be assigned (you'd be obligated to deliver/take shares). There is no Securities Transaction Tax in the UK. Always close 1-2 days before front expiry to avoid pin/gamma and assignment complications.

Calendar spreads are debit strategies, so the capital requirement is just the premium paid. For FTSE 100 ATM calendars, expect roughly 80-180 points debit per contract (GBP 800-1,800 at GBP 10 per point). A recommended minimum trading capital is around GBP 10,000+ to properly diversify across 2-3 positions while keeping each position under 10% of capital.

At the same ATM strike, call and put calendars have nearly identical risk-reward due to put-call parity. Choose based on: 1) liquidity - whichever has tighter spreads, 2) a slight directional bias - calls if mildly bullish, puts if mildly bearish, 3) skew - sometimes puts are cheaper due to elevated put IV. For most beginners trading ATM strikes, the difference is negligible.

Compare the IV of your specific strikes across expiries, not just the headline index volatility. Front month IV should be equal to or higher than back month IV (flat to backwardated). Most option chains show IV per strike. Calculate the IV ratio: front IV / back IV. Ratios above 1.0 are favorable; below 0.95 is unfavorable. Also check the IV percentile for each expiry - a high front month percentile with a lower back month percentile is ideal.

Roll when: 1) the position is at or above breakeven, 2) your thesis of range-bound price action remains valid, 3) you can roll for reasonable cost (not more than 25% of remaining position value), 4) the back month still has adequate time remaining (>20 DTE after the roll). Close when: 1) the position is losing significantly, 2) the thesis has changed (expecting a breakout), 3) the roll cost is excessive, 4) you're approaching the profit target anyway.

Events between expiries create complex IV dynamics. Front month IV may be depressed (the event is after that expiry) while back month IV is elevated (the event falls in that period). This 'IV kink' in the term structure can hurt calendars - you're selling cheap IV and buying expensive IV. Generally avoid calendars when a major event (results, BoE, the Budget) falls in the back month period. If the event is after both expiries, the effect is minimal.

Yes, calendars offer flexibility. You can: 1) convert to a diagonal by moving the short strike (adjusts directional exposure), 2) convert to a double calendar by adding another calendar at a different strike, 3) convert to a butterfly by adding another short at the same expiry as the front (changes to single-expiry), 4) simply close the front leg to remain with a naked long option. Each conversion has trade-offs; evaluate based on the new market outlook.

Near front expiry, the short front month option experiences extreme gamma (rate of delta change). Small price moves cause large delta swings. Theta accelerates but gamma risk often outweighs the theta benefit. Vega collapses in the front month while remaining stable in the back month, changing your net vega exposure. This Greek instability is why experts close or roll 3-5 days before front expiry - the edge from theta no longer compensates for gamma risk.

To profit from term structure steepening (back month IV rising relative to front), enter calendars when the structure is flat or slightly backwardated. The ideal is catching the transition from backwardation to contango. Structure positions with higher vega sensitivity in the back month by selecting strikes where back month vega is 1.5-2x front month vega. Consider a longer back month duration (50-60 DTE vs 40 DTE) for greater vega exposure. Exit when the term structure reaches the target contango level.

Portfolio-level management focuses on aggregate Greeks. Target delta neutrality at portfolio level (+/-5% of notional). Limit total negative gamma to an amount where a 2% underlying move produces an acceptable P&L impact. Maintain positive theta sufficient to cover expected transaction costs plus a target daily profit. Vega should align with your IV forecast - reduce it if you expect an IV crush. Rebalance when any Greek exceeds its threshold rather than at fixed time intervals.

Vol arb traders identify mispricings in the IV term structure relative to realized vol expectations. When front month IV is high relative to expected realized vol, sell calendars (sell back, buy front) to short vol. When back month IV is cheap relative to forward vol expectations, buy calendars. The key is having accurate realized vol forecasts. Professionals use transparent statistical models they compute and inspect themselves (for example GARCH or HAR-RV) to forecast realized vol and compare it against the implied term structure - these are classical statistical tools, not automated or AI-driven trading systems.

Correlation-adjusted sizing is essential. Calendars on the same underlying are highly correlated - treat FTSE 100 calendars at different strikes as 60-70% correlated. Index calendars (FTSE 100 vs FTSE 250) are 70-80% correlated. Calculate portfolio VaR including correlations. Limit single-underlying exposure to 25% of total calendar capital. Limit total positive vega such that a 5-point VIX/VSTOXX drop doesn't cause a >10% portfolio loss. Stress test against 2008, 2020-style vol regime changes.

Track and analyze: 1) entry IV percentile - win rate by front and back IV percentile buckets, 2) term structure slope at entry - win rate by IV differential, 3) days held vs initial DTE - optimal exit timing, 4) realized vs implied vol ratio during the trade - edge source analysis, 5) gamma-adjusted returns - are profits from theta or from lucky price stability? After 50+ trades, identify which conditions produce a statistical edge. Abandon variants without a demonstrable edge despite a favorable sample size.