heres your situation, you have either a covered call position or diagonal spread position on AAPL and are unsure of when to roll that short call to the next month. i really dont like bloggers that feel they have to talk in "option greeks" to make themselves feel smart, so ill keep it to a minimum. Assume you have the following:
Short the June 600 call at $6.00
you are looking to roll it to the July 600short call at $18.00
so at first glance you see that by rolling today you gain a credit of $12 ($1200) per contract. things to consider with 17days left to june opex..
Notice the time decay of each option (the theta column):
June600 is -.36 and the July600is -.25 .. meaning june is decaying .36cents a day vs .25cents a day for July..no shit right, front month decays faster..but that means that by holding off on rolling that difference works 11cents in your favor each day..so all other things being equal, the call you could roll today for $12 will be able to be rolled tomorrow for $12.11 .. so 11cents in your favor, this number will increase in your favor as decay speeds up on front month.
The other major factor in that pricing is the IV movement, as you know going into an event, earnings usually, the IV increases..so despite time decay working the option will likely increase in value the closer to the earnings date you go..in this case the unconfirmed earnings date of 17july for AAPL.. so IV will slowly start creeping up the closer you get to that date...that increase will start to offset that time decay..so you have 2 things working for you to keep the price of the july call higher the longer you wait.
These are just 2 things to consider when making your decision on whether to roll that short call now or wait.. it is not the be all end all .