You're adding Timezone offset for your PC to the local time on the same PC. The local time has that offset already applied to it.
You can get GMT/UTC time as comment in the code says

? DATETIME() + lnTimeZoneOffset

>Yes, I know I'm posting to myself. Doug must be busy, but I really need to figure this out. Can anyone see in the code why it would offset by 4 hours rather than just return the current date and time since it's all in the same time zone?
>

>
>* You can then add lnTimeZoneOffset to a local time value to get a time in Greenwich
>* Mean Time (GMT) or subtract lnTimeZoneOffset from a time value in GMT to obtain a
>* local time value.
>
>? DATETIME() - lnTimeZoneOffset
>