Quote from spindr0:
They're the same.
An easy way to see this is to model the positions. Buy the OTM calendar and sell the ITM calendar. Use fair prices. The graph over time and price will be a straight line at ZERO indicating that there's no potential gain or loss. That means that the positions are synthetically equivalent - what one makes, the other loses and vice versa.
yes,at first look they are the same.....syntetics......but if you look deeper,there will be for sure a difference....because of the volatility change.
OTM put callendar will gain more than the ITM call during the fall,because most of the time with a fall volat. rises and will apriciate the OTM spread more,than the ITM......till the the fall gets to the strike of the spread.
expecially if a trader is hedged and wants to get out of the spread before the underline hits the strike,OTM put is the better choice,not because of something else,but because of the spike in IV if the move occures.
ectually ITM callendars is good to be used ,when looking for uptrend.
with the rise of the underline,IV ussually falls,so part of the gain of the OTM call callendar is eaten off from the fall of IV......so in that case is better to use ITM put callendar......

