I'm an amateur observer of this, but speaking in centuries rather than decades I can tell you that Old Spanish up until a little bit after the time of Columbus had different phonetics for several consonants, and thus different spelling. eg. There was a /ʃ/ sound spelled with X, as well as a /ʒ/ which was spelled with J or GI, GE -- this all merged and is today spelt with J or GI, GE, pronounced [x]. Also what is today /θ/ in Spain was once distinct /ts/ and /dz/, written as ç and z respectively (today c and z). /b/ and /v/ had not yet merged and their spellings have since been sort of "re-based" to look like their Latin roots. <h> for a time was not silent, and many words that start with <h> used to have an /f/.
So, the interesting thing about this relative to English: when pronunciation changed around 1500, they also updated the spelling.