Due Date for Profit Sharing Contributions to be Deductible (September 15?)

I was always told/taught that receivable profit sharing contributions are due the earlier of:

1) September 15
2) The date you file your tax return

In researching something, I just found this on the IRS website:

For example, if the due date of the employer's calendar-year 2022 Form 1040 or Form 1120 is April 18, 2023, with an extended due date of October 16, 2023 (after the automatic six-month extension), the employer has until October 16, 2023, to make a 2022 profit-sharing contribution and deduct it on their 2022 return.

Have I always been taught the wrong thing?  Or am I confusing two different things?  Now I'm confused, but is this an instance that if the company is a C-Corp you do have until October 15 to fund the contribution?

Thanks in advance!

I think the issue is the due date for C corp tax returns changed back in 2016 or so.  It used to be they were due 3/15 so 6 months afterwards was 9/15.

See this link

https://www.cpa-wfy.com/get-ready-businesses-some-filing-due-dates-are-changing/

I quote (bold mine):

For many years, C corporation federal income tax returns on Form 1120 were due two and a half months after the end of the corporation’s taxable year (March 15, adjusted for weekends and holidays, for a calendar-year corporation). Form 1120 could be automatically extended for six months (through September 15, adjusted for weekends and holidays, for a calendar-year corporation).

However, a law passed last year established new due dates for Form 1120. For tax years beginning after December 31, 2015, the due date is generally moved back one month to three and a half months after the close of the corporation’s tax year (to April 15, adjusted for weekends and holidays, for a calendar-year corporation).

So someone taught you a short hand version of the rule and never taught you why is was 3/15 and 9/15.  So when the due date of the 1120 changed you didn't pick up on it changing the deduction deadline. 

Zeller's way of saying it is the better way to teach it and that hasn't ever changed.   

My go-to when I need a refresher is this article:

https://www.nfp.com/insights/what-is-the-real-deadline-for-making-plan-contributions/

That was a good article, and it went into a lot of the what-ifs with the 415 limits per year....I wish it had addressed what happens if the 2023 SH deposit is indeed made 12/31/24 (as in one of its examples) and it's for someone with a $0 annual additions limit at all for 2024 because they had terminated employment in 2023.