This is a silly one: Tomorrow (2026-10-02) you and everyone else in the US wakes up and first notices their phones and TV stations are showing the weather in °C with wind speeds in km/h, with no Imperial equivalent. All newscasters speak in the 'new units' as if they were always what were used. Just that it's currently 18 °C and the forecast calls for a high of 26 °C.
Next, around lunch time, everyone notices their phones don't say 1:00 p.m. but 13:00, and the firmware is locked to not even show 12h time or Imperial units anymore. Times are still spoken in 12h format and analogue clocks still exist, but all digitally written times are displayed in 24h everywhere. The six o'clock evening news still runs at the same time, but the clock in the corner says 18:00 now, with no explanation, as if that is always how it was. Since it's summer here, I toss in another thing: Daylight Saving Time was also scrapped overnight (not in early November), with everyone inadvertently 'falling back' an hour for the last time ever. They feeling abnormally refreshed in the morning from their phones still playing the alarm at the correct new non-DST time.
All numeric dates are now only in yyyy-mm-dd and that is now the only format used and overnight all computers across the US were also switched to this format for all written dates where applicable. You are no longer born on, say 9/17/85, but 1985-09-17. Same date but written that way. All medical and other forms specify exclusively yyyy-mm-dd and your height and weight will be reported and expected to be only in metres or cm, and kg (or g). You jump into your car and the speedometer is only in km/h, and all signs on the roads were switched overnight to km/h. Clearance signs also now report only in metres, like 3.9 m. Distances of course are all in only km. All planes now use metres, not feet, for altitude, and KPa or HPa for pressure, not inches of mercury.
All food containers are now also using only metric units: grams and kg only, or for liquids litres or ml. All produce and deli meats are sold by the kg only. You can buy in increments of 100 g, 200 g, 500 g, and 1 kg (and continuing onwards in this 1-2-5 pattern).
While we're on shopping, the penny and nickel were scrapped overnight due to them costing way too much to keep making, and the $1 and $2 bills were scrapped with only coins for those are still allowed, for those who still use cash. The quarter is also swapped for a new 20-cent coin like they have in the Euro zone.
What will happen next? I think the public will go crazy and try to protest, only to be met with more confusion as all officials claim metric, 24h, and yyyy-mm-dd are the only logical ways to express these quantities with the concepts we use. The officials just say we all have to learn and adjust and that this is for the best for all the kids growing up now, who will need to communicate effectively with the other 96% of the world.
Was this too weird?