Indian Chronology (Solar, Lunar and Planetary): A Practical Guide to the Interpretation and Verification of Tithis, Nakshatras, Horoscopes and other Indian Time-records, B.C. 1 to A.D. 2000 c23.17

c23.17

"It is well to note that where the first tithi of a month ends not less than 5 ghatikas before sunset, the heliacal rising of the moon will probably take place on the same evening; but where the first tithi ends 5 ghatikas or more after sunset, the heliacal rising will probably not take place till the following evening. When the first tithi ends within these two periods between 5 ghatikas before and 5 ghatikas after sunset, the day of the heliacal rising can only be ascertained by elaborate calculations".