SITUATION BEFORE (with faults):
On my PC I use timezone GMT+1 (Amsterdam).
When I sync my phone, all appointment times are correct on the standard calendar app (Android Calendar).
On the phone I use also GMT+1 (i.e. same as on PC).
Smooth Calendar shows times are 1 hour earlier.
Now I change the timezone on phone to GMT+2.
Now times on both calendars are correct.
Only the phone clock is 1 hour later.
Therefor change the phone clock to the correct time.
And uncheck the auto update with network.
Result : all times OK.
Quirk : use of different timezones on PC vs. phone.