Every long vowel in English quietly shifted shape over 300 years, unrecorded

Between roughly the 1400s and 1700s, English speakers gradually shifted the pronunciation of long vowels, so that the word 'bite', once pronounced like 'beet', ended up sounding nothing like its Middle English form. The shift is why English spelling, frozen before the change, looks so disconnected from how the words are actually said today.

— Historical linguistics record, Great Vowel Shift — English phonological change, c. 1400-1700