I successfully tested the settings above in sys.txt and they work fine in my nextgen israel (gift), with procedure below:

1. Made route and checked alternatives;
2. Left route active, closed nextgen, modified sys with different start hour/day;
3. Started nextgen and the alternative routes were the same. With route active this means the software does not recalculate.
4. Canceled route and then recreated same route. This time alternatives were different (and different arrival time). So the route must be recreated.

So, in case you make ux, must be inserted some string that triggeres also recalculate after setting the departure day/hour.

Thanks!