In Tenpo-reki, Teikiho (a way of expressing 24 divisions of the old calendar) was used, which is the method to calculate the position of the sun and divide the orbit of the sun on the celestial sphere by twenty-four (divide in the space) to obtain 24 divisions of the old calendar.
天保暦では太陽の位置を計算し、天球上の太陽の軌道を24等分（空間分割）して二十四節気を求める「定気法」を採用した。