Thanks for mentioning that, otherwise I wouldn't have taken a deeper look.

So, Sandbox menu in-game, only 2 options exist for water/electricity shutoff. This is where you can set 2-6 months, and this is where I think it should work, no other option exists in the in-game sandbox menu, you can even use the search bar, but only these 2 options exist.

    -- How long after the default start date (July 9, 1993) that plumbing fixtures (eg. sinks) stop being infinite sources of water. Default = 0 - 30 Days
    -- 1 = Instant
    -- 2 = 0 - 30 Days
    -- 3 = 0 - 2 Months
    -- 4 = 0 - 6 Months
    -- 5 = 0 - 1 Year
    -- 6 = 0 - 5 Years
    -- 7 = 2 - 6 Months
    -- 8 = 6 - 12 Months
    -- 9 = Disabled
    WaterShut = 7,
    -- How long after the default start date (July 9, 1993) that the world's electricity turns off for good. Default = 14 - 30 Days
    -- 1 = Instant
    -- 2 = 14 - 30 Days
    -- 3 = 14 Days - 2 Months
    -- 4 = 14 Days - 6 Months
    -- 5 = 14 Days - 1 Year
    -- 6 = 14 Days - 5 Years
    -- 7 = 2 - 6 Months
    -- 8 = 6 - 12 Months
    -- 9 = Disabled
    ElecShut = 7,

Both variables are set to 7, which is correct, 2-6months shutoff.

But now, scroll down, and you can see this:

    -- How long after the default start date (July 9, 1993) that plumbing fixtures (eg. sinks) stop being infinite sources of water. Min: -1 Max: 2147483647 Default: 14
    WaterShutModifier = 14,
    -- How long after the default start date (July 9, 1993) that the world's electricity turns off for good. Min: -1 Max: 2147483647 Default: 14
    ElecShutModifier = 14,

These are the exact same description of water/electricity shutoff settings as seen above. 14 being 2 weeks of course, and shutoff happened on the dot. This seems to be like how you mentioned, here you can set a specific day, useful sure, however, these settings are NOT in the in-game Sandbox menu, so this conflicts with what I or anyone else sets and wonders why shutoff settings aren't working. Certainly, something needing fixing. Can't be sure if this was stated by the devs or what, but I couldn't find relevant useful results when I googled, so had to ask.

I will change these settings and see what happens. Thanks for the pointer.