trial version in vfp

[eyeshield21]

what is the easiest way to create a demo which will expire after such and
such days?
and also to prevent the user to change system date

 

[Tore Bleken]

If the URL is buried deep inside an exe, how will the user know? And secondly, if you have users who are able to do this, would they be your customer in the first place? No, they would make it themselves.

 

[Olaf Doschke]

Well, you never know the topic of the application. Just being able to set up a proxy or redirect via hosts you still wouldn't be able to do any application which needs some expert knowledge on any topic.

Bye, Olaf.

 

[Dan Olsson]

I don't understand the problem with time-offsets.
For a trial a couple of hours more or less does not matter, right?

 

[Olaf Doschke]

Dr Dolittle,

I already said:

To get the 30 day trial expiration you won't need to convert to local time at all, but it's obviously a nice addition to be able to see whether the system clock is not in sync with real local time. Well, at least if the system time zone os set correctly.

So, yes, the offset doesn't matter, but that was just a side topic anyway. And you might detect somebody trying to fool you and could react to that. You'd have to accept some inaccuracy of system time vs time you get from the internet, but if you make a mistake with bias you'd always detect tempering with the time where there really isn't.

Bye, Olaf.

 

[JRB-Bldr]

I have to agree with drdolittle - although for a somewhat different reason.

If the StartDateTime were captured at Installation as UTC time (no bias offset used)
And the CheckDateTime was also in UTC time (no bias offset used)

Then the difference is merely the CheckDateTime - StartDateTime and the SNTP DateTime bias/offset need not be used.

Good Luck,
JRB-Bldr

 

[Olaf Doschke]

As said:

you won't need to convert to local time at all

Making the same offset error twice you make no error, especially since UTC does not switch to DST.
It's not a somewhat different reason, it's exactly my and dr dolittles point.

I just also gave a reason to apply the right bias as check of the system time against real local time.

Bye, Olaf.

 

[eyeshield21]

tnx for the reply.
..youre very helpful..
.i chose to limit the entry on the table as suggested...