Look at these examples from an extended sequence from April, 2016.
This sequence is full of meta references. As Ted notes, the strip used to be just a gag-a-day comic. Sally comments on how Marciuliano more fully develops the characters and situations. In the final panel, Ted almost seems aware of the reader, but Sally defuses it with the punchline.
In the first panel, Ted says it's been almost 24 years since their first date (which took place while they were in college) -- 1992. Sally remarks that their timeline doesn't bear close examination. Which is true. When the strip started in 1982, their daughter Hillary was 12 years old (and still is). That pushes that first date back to 1970 at the earliest.
Ted's right -- Hillary's last name is in the title of the strip.
And yes, Sally's final observation, while seemingly comic exaggeration, isn't. The sequence at the restaurant did indeed take two weeks of strips to tell.
Personally, I enjoy the extra dimension Marciuliano gives to the strip with these meta-observations. It's made Greg Howard's original creation even better -- and certainly more rewarding to read on a daily basis.