Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 6 · Calendar, Muhurta Elements
कालमानं मुहूर्ताङ्गानि च
लंकोदयात्स्याद्वारादिस्तस्मादूर्ध्वमधोऽपिवा ।देशांतरस्वचरार्द्धनाडीभिरपरे भवेत् ॥ १५९ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 159.
The weekday begins at sunrise at Lanka. At other places it begins later or earlier. The gap is counted in ghatikas (24-minute unit). It comes from the distance in longitude and from the place's own charardha (sunrise shift from day length).
Simple meaning: The weekday begins at sunrise in Lanka. Elsewhere it starts later or earlier by a set amount.
बलप्रदस्य खेटस्य कर्म सिद्धचति यत्कृतम् ।
Work tied to a strong planet succeeds. Under a weak planet it fails, even with effort.
इंदुज्ञजीवशुक्राणां वासराः सर्वकर्मसु ।
The Moon, Mercury, Jupiter and Venus days suit all work. The other days suit only harsh work.
रक्तवर्णौ रविश्चंद्रौ गौरो भौमस्तु लोहितः ।
Each planet has a colour: Sun red, Moon white, Mars blood red, Mercury green, Jupiter yellow, Venus white.