Do Tide and Current Displays in OpenPCN assume the PC is set to local zone time in each of the time zones you voyage through? The alternative would be UTC.
And is it so that OpenCPN makes no correction for Daylight Saving Time so the PC time has to provide the unaltered zone time.
Times in tides are in local time.
If your computer operating system is not set to the local timezone O can't know the the time zone you are currently using.
On the tidalgraph the currently used timezone is displayed underneath the hours line.