Learn English – What does “do’t” mean

The phrase "this will date me" is often used when referring to something that you would/could only know about if you are old. "This" is referring to whatever example or topic you are about to say. It's almost always used before referencing some kind of outdated technology, method, or historical event.

See definitions 16 and 17 here.

16. "Date" (verb): to ascertain or fix the period or point in time of; assign a period or point in time to

17. "Date" (verb): to show the age of; show to be old-fashioned

For example, if you are going to talk about how to play music, you might say, "This will date me, but we used to have to place a needle on the physical record. Now you can just tap your phone and music will play."

It's like a kind of joke about your own age. It's equivalent to saying "this will show how old I am". It plays off of the idea that people, in general, like to appear young or youthful. The phrase is sort of "admitting" that you are old before outright giving it away by the example you are going to use.

When talking about the "undo" feature on a computer, "This will date me, but when I was using a typewriter I had to be very careful about making mistakes."

If that was said by a non-native speaker, it sounds like they are hoping you plan goes smoothly, meaning you don't experience any bumps (problems) executing the plan.

For clarity, this is not how a native speaker would express this, but it's easily understandable.

It's similar to saying

They run a smooth operation.

meaning things just work without problems or complications.