The 14th Century

The ruling class began to use Middle English increasingly around this time. The Parliament of England used English from about the 1360s, and the king's court used mainly English from the time of King Henry V (who acceded in 1413). The oldest surviving correspondence in English, by Sir John Hawk wood, dates from the 1390s. With some standardization of the language, English began to exhibit the more recognizable forms of grammar and syntax that would form the basis of future standard dialects:
And it is don, aftirward Jesus made iourne bi cites & castelis prechende & euangelisende þe rewme of god, & twelue wiþ hym & summe wymmen þat weren helid of wicke spiritis & sicnesses, marie þat is clepid maudeleyn, of whom seuene deuelis wenten out & Jone þe wif off chusi procuratour of eroude, & susanne & manye oþere þat mynystreden to hym of her facultes
—Luke ch.8, v.1–3

"And it came to pass afterward, that he went throughout every city and village, preaching and showing the glad tidings of the kingdom of God: and the twelve were with him, and certain women, which had been healed of evil spirits and infirmities, Mary called Magdalene, out of whom went seven devils, and Joanna the wife of Chuza Herod's steward, and Susanna, and many others, which ministered unto him of their substance."
—Translation of Luke ch.8 v.1–3, from the New Testament

A text from 1391: Geoffrey Chaucer's Treatise on the Astrolabe.

This was a time of upheaval in England. Four kings were deposed between 1399 and 1500, and one of them was deposed twice. New men came into positions of power, some of them from other parts of the country or from lower levels in society. Stability came only gradually, after 1485, with the Tudor dynasty. The language changed too—there was much change during the 15th century. But towards the end of that century more modern English was starting to emerge. Printing began in England in the 1470s, which tended to stabilize the language. With a standardized, printed English Bible and Prayer Book being read to church congregations from the 1540s onward, a wider public became familiar with a standard language, and the era of Modern English was under way.