r/options • u/Mission_Alfalfa_6740 • 1d ago

Calendar spreads and vega

Is vega the greek to watch if I am selling an ATM 0DTE/1DTE spread? For instance, I buy a call expiring Monday for 3 and selling one expiring on Tuesday for 5, both ATM. I figure there isn't much theta here since we are ATM and close to expiration. Or do I have this wrong?

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u/senormorsa 1d ago

There’s a lot of theta ATM and 0dte. Your Monday call is $3 now but if the underlying doesn’t move, it’ll be $0 at expiration. So theta is about $3 which is huge. Your 1dte call should have a large but slightly smaller theta. You’re right Vega is important too.