यदा यदा हि धर्मस्य ग्लानिर्भवति भारत।
अभ्युत्थानमधर्मस्य तदाऽऽत्मानं सृजाम्यहम्।।4.7।।
।।4.7।।हे भरतवंशी अर्जुन जबजब धर्मकी हानि और अधर्मकी वृद्धि होती है तबतब ही मैं अपनेआपको साकाररूपसे प्रकट करता हूँ।
No fixed time schedule has been mandated for Lord Krishna to manifest Himself in His avatar forms or authorised incarnations but he declares beginning with yada yada which means that: whenever or wherever dharma or righteousness as ordained by the Vedic scriptures under varnasrama or the four stages and position in Vedic culture become degraded and unrighteousness increases and becomes dominant at that time Lord Krishna or any of His authorised incarnations descends and becomes manifest. It should be noted that all the names of His avatars or incarnations are recorded in the Bhagavat Purana and othe Vedic scriptures with additional details so that it can be proven when His divine incarnation has manifested.