Talk:1079

Incorrect claim of Khayyam's measurement

The article claims that Omar Khayyam measured the length of the year to 365.24219858156 days. This appears to be an Internet legend based on a mistaken algorithmic version of the calendar. No historical sources have been found that can confirm the claim. Not to mention that it is logically incorrect, as his actual measurement (365.2424…) is impressively close to the current mean vernal-equinox year, which is what matters for a calendar that uses the vernal equinox as its reference point. His real achievement is just this – it is the most precise calendar in use today, much more accurate than the Gregorian calendar some 500 years later.

In A concise review of the Iranian calendar, M. Heydari-Malayeri writes: "Note that recently an extremely precise value for the duration of the year (365.24219858156 days) has been attributed to Khayyâm (O'Connor & Robertson 1999), although it is supported by no historical source, as far as we know. We think that this may be a spurious value resulting from the erroneous 2820-year cycle suggested recently (see below Section 7)." — Preceding unsigned comment added by Joakims (talk • contribs)