Railway time and ordinary time

Railway time was the standardised time arrangement first applied by the Great Western Railway in England in November 1840, the first recorded occasion when different local mean times were synchronised and a single standard time applied. Railway time was progressively taken up by all railway companies in Great Britain over the following two to three years. The schedules by which trains were organised and the time station clocks displayed were brought in line with the local mean time for London or "London Time", the time set at Greenwich by the Royal Observatory, which was already widely known as Greenwich Mean Time (GMT).

Ordinary Time comprises two periods of time in the Christian liturgical year that are found in the calendar of the ordinary form of the Roman Rite of the Catholic Church, as well as some other churches of Western Christianity, including those that use the Revised Common Lectionary: the Anglican Communion, Methodist churches, Lutheran churches, Old Catholic churches and Reformed churches.In Latin, the name of this time is tempus per annum translated as time during the year.The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods:[1] a.m. (from the Latin, ante meridiem, meaning before midday) and p.m. (post meridiem, meaning after midday)

In several countries the 12-hour clock is the dominant written and spoken system of time. Other countries use the 12-hour clock mainly in spoken time, while the24-hour notation is written. In most countries the 12-hour clock is used in speech alongside the 24-hour clock.

The 24-hour clock is the convention of time keeping in which the day runs from midnight to midnight and is divided into 24 hours, indicated by the hours passed since midnight, from 0 to 23. This system is the most commonly used time notation in the world today,[1] and is used by international standard ISO 8601.

A time of day is written in the 24-hour notation in the form hh:mm (for example 01:23) or hh:mm:ss (for example, 01:23:45), where hh (00 to 23) is the number of full hours that have passed since midnight, mm (00 to 59) is the number of full minutes that have passed since the last full hour, and ss (00 to 59) is the number of seconds since the last full minute.