...in fall, clocks fall back from 1:59 a.m. to 1:00 a.m.
In the U.S., restaurants and bars have various closing policies. In many states, liquor cannot be served after 2:00 a.m. But at 2:00 a.m. in the fall, the time switches back one hour. So, can they serve alcohol for that additional hour in October?
The official answer is that the bars do not close at 2:00 a.m., but actually at 1:59 a.m. So, they are already closed when the time changes from Daylight Saving Time into Standard Time.
In practice, however, many establishments stay open an extra hour in the fall.
In the U.S., 2:00 a.m. was originally chosen as the changeover time because it was practical and minimized disruption. Most people were at home and this was the time when the fewest trains were running. It is late enough to minimally affect bars and restaurants, and it prevents the day from switching to yesterday, which would be confusing. It is early enough that the entire continental U.S. switches by daybreak, and the changeover occurs before most early shift workers and early churchgoers (particularly on Easter) are affected.