Verified Trial - Expiring

Custom license fields are just extra data that is sent along & signed along with the other activation data. That is, the customer can activate the key and the license fields are sent along no matter what is contained in the fields. So even if you have a "trial_expires" license field, and the date has long since passed, the use will still be able to activate the product key. However, your app will actually check the license field "trial_expires" and see the date has passed. From there you can do whatever you want: let the user extend their trial, or prompt them to buy your app, etc.

Thanks for the answer. However, I made a mistake, i didn't saw there 3 kind of trial, regular trial, trial extension and verified trial. My question was meant for the trial extension.

So which case apply for the expiration date of the trial extension ?

I'm not sure what you're asking. Are you asking about the "Trial extension expires" value? If so, the page explains:

When this trial extension can no longer be used (default: 2 weeks from now).

In other words, if the user tries to use the trial extension after the date you use then it won't work. It has nothing to do with the length of the trial.

Ok, so someone activating the trial extension 2 days before it expire, will have a maximum of 2 days of use even if the trial length is 10 days.

It is not a maximum date for activation. It is for both activation and use.

Trial extensions aren't activations. Trial extensions can be shared very easily. They're part of the unverified trials (a.k.a. quick & dirty trials).

the trial extension 2 days before it expire, will have a maximum of 2 days of use even if the trial length is 10 days.

No. They will get 10 days. They will get 10 days no matter what. Unless the "expired" date has been reached. In that case they'll get 0 days.