GetDaysToExpiration() returns the WRONG number

[KohPhiPhi]

I have created a very simple custom script that should display the number of days to expiration as a column in the option chain. I use the GetDaysToExpiration() function. The platform shows that as of today (Dec 15th 2023), there are 280 days left to the expiration Sep 20th 2024). Therefore, I was expecting the script to display "280" for all the strikes within that expiration date.

THE PROBLEM IS... the function is displaying "282" for most strikes, and sometimes it displays other RANDOM numbers for different strikes within the SAME expiration date!!! It's like the function GetDaysToExpiration() itself was broken.

Please see the two screenshots attached.

Any idea how I can get the accurate number of days to expiration? Thanks!

 

[Joshua]

It's giving you the days to expiration from the last time the option actually traded, which is not necessarily today's date, and some options have never traded yet at all. The blank option data going forward, at least relative to the underlying, takes some coercion to be evaluated. Bear in mind, the solutions to these issues with custom options columns are generally unstable, and prone to periodic failure, N/A, and Loading...

def Under =
    Close(getunderlyingSymbol());
def Extra; def Fetch; def Days;
if !isNaN(close) and isNaN(close[-1]) {
    Extra =
        fold index = 0 to 49
        with data = 0
        while !isNaN(data)
        do
        if !IsNaN(GetValue(Under,-index)) then index
        else data;
    Fetch =
        GetValue(GetyYYYMMDD(),-Extra);
    Days =
        getdaysToExpiration() - daysTillDate(Fetch) - 1;  
} else {
    Extra = Extra[1];
    Fetch = Fetch[1];
    Days = Days[1];
}
plot Column =
    if Days > 10000 then Days - 19725 else days;

 

[KohPhiPhi]

It's giving you the days to expiration from the last time the option actually traded, which is not necessarily today's date, and some options have never traded yet at all. The blank option data going forward, at least relative to the underlying, takes some coercion to be evaluated. Bear in mind, the solutions to these issues with custom options columns are generally unstable, and prone to periodic failure, N/A, and Loading...

Very useful post, thank you Joshua.

It's VERY strange that ThinkOrSwim doesn't have a simple function to retrieve the number of days left to expiration, forcing us to use patchy work arounds. I wonder why?

At any rate, thank you again!