AM and PM are associated with 12-hour timekeeping, as opposed to the international 24-hour clock. The 12-hour system grew up mainly in Northern Europe, and spread globally from there via the British Empire.
The adjective STRENUOUS has 2 senses: 1. characterized by or performed with much energy or force. 2. taxing to the utmost; testing powers of endurance. Familiarity information: STRENUOUS used as an adjective is rare.
He was a strenuous advocate of reform, especially in the teaching of sciences, and supported the claims of modern languages to a place in the curriculum. Frequently half his nights were spent in reading, after the labour of his most strenuous days.