What's the Difference Between Tojeong Bigyeol and Saju?

They calculate in different ways. Tojeong Bigyeol plugs your birth date into a fixed formula to draw a hexagram (卦), while Saju converts the year, month, day, and hour of your birth into eight characters (stem-branch pairs) using the Ten-Thousand-Year calendar. We don't claim one is more accurate than the other — both are a matter of reference, not a fixed fate.

How exactly do the calculation methods differ?

Saju converts your birth moment into Sixty Gapja stem-branch pairs via the Ten-Thousand-Year calendar, raising four pillars and eight characters. Even the boundaries of the year and month are set by solar terms rather than calendar dates. Tojeong Bigyeol, instead of raising eight characters, plugs the numbers of your birth date into a formula to get a single hexagram, then reads the interpretation attached to it. It's traditionally a book people opened around the New Year (Jeongwol).

Which one is more accurate?

We don't rank them. They simply rest on different calculation systems. On the Saju side, because it's Ten-Thousand-Year calendar math, the same birth date always produces the same chart — meaning it's calendar calculation you can check yourself. You can read more on what basis Saju measures time in not the lunar or solar calendar, but solar terms, and about the character that stands for "you" among the eight in the Day Master.