The two 15° halves
Each sidereal rāśi is split into a first half from 0° to less than 15° and a second half from 15° to less than 30°. For the six odd signs—Aries, Gemini, Leo, Libra, Sagittarius, Aquarius—the first half belongs to Sun Hora and the second to Moon Hora. For the six even signs, the order reverses. Exactly 15° starts the second half. The historical rule appears in Bṛhat Parāśara Horā Śāstra 6.6 and Bṛhat Jātaka 1.12.
This calculator displays Sun Hora placements in Leo and Moon Hora placements in Cancer. That common two-sign rendering is a chosen chart convention, not the only D2 layout. The source verse establishes Sun/Moon ownership of each half; it does not settle every later D2 sign mapping. The tool first calculates D1 positions with Astronomy Engine 2.1.19 and this site's approximate Lahiri ayanamsha, then applies the selected D2 rule.
Read D1 with D2
The results retain each D1 rāśi and degree beside the derived Hora lord and Cancer or Leo display placement. The D2 display degree stretches a 15° interval to 30° so positions can be shown in a two-sign diagram. Check the method guide before comparing other D2 websites, which may use a different Hora convention.