When did days first start at midnight?

Answer 1

The convention of starting days at midnight began in the late 19th century, primarily with the adoption of standardized timekeeping practices. Before that, days were often defined by sunrise to sunrise or sunset to sunset, depending on local customs. The shift to a midnight start was solidified with the introduction of the 24-hour clock and the widespread use of railroads and telegraphs, which required more precise scheduling. By the early 20th century, midnight as the start of the day became widely accepted.