600 years (since Middle English), while omitting any detail in the Old English and earlier periods. For more detail about the changes in the first millennium AD, see the section on the development of Old English vowels. This table omits the history of Middle English diphthongs; see that link for a table summarizing the developments. The table is organized around the pronunciation of Late Middle English c. 1400 AD (the time of Chaucer) and the modern spelling system, which dates from the same time and closely approximates the pronunciation of the time. Modern English spelling originates in the spelling conventions of Middle English scribes and its modern form was largely determined by William Caxton, the first English printer (beginning in 1476). As an example, the vowel spelled corresponds to two Middle English pronunciations: in most circumstances, but long in an open syllable, i.e. followed by a single consonant and then a vowel, notated aCV in the spelling column. (This discussion ignores the effect of trisyllabic laxing.) The lengthened variant is due to the Early Middle English process of open-syllable lengthening; this is indicated by (leng.). Prior to that time, both vowels were pronounced the same, as a short vowel ; this is reflected by the fact that there is a single merged field corresponding to both Middle English sounds in the Late Old English column (the first column). However, this earlier Middle English vowel is itself the merger of a number of different Anglian Old English sounds: the short vowels indicated in Old English spelling as , and ; the long equivalents , , and often when directly followed by two or more consonants (indicated by ā+CC, ǣ+CC, etc.); occasionally, the long vowel when directly followed by two consonants, particularly when this vowel corresponded to West Saxon Old English . (Middle English, and hence Modern English, largely derives from the Anglian dialect of Old English, but some words are derived from the West Saxon dialect of Old English, because the border between the two dialects ran through the London area. The West Saxon dialect, not the Anglian dialect, is the "standard" dialect described in typical reference works on Old English.) Moving forward in time, the two Middle English vowels and correspond directly to the two vowels and , respectively, in the Early Modern English of c. 1600 AD (the time of Shakespeare). However, each vowel has split into a number