In this block, lunar days are calculated in a given time range. There are 3 variants of algorithms:

- Moonrise – Every lunar day begins with the moonrise. The first lunar day begins at the moment of the new moon;
- Babylonian – the distance between the ecliptic coordinates of the Moon during neighboring syzygies is measured, 360° is added to them, and the resulting sum is divided by 30. This will be the step by which the Moon will advance each lunar day, and the time calculated for each such advance, and will be the time of the beginning of the next lunar day;
- Symbolic – the time between neighboring new moons is divided by 30. Thus, it turns out exactly 30 lunar days per synodic month;
- Tithi – the length of time between lunar days (Tithi) corresponds to the longitudinal angle between the Sun and the Moon, a multiple of 12°. Tithi begins at different times of the day and lasts from about 19 to 26 hours. The cycle begins at the new moon.