यदा मेषतुलयोर्वर्तते तदाहोरात्राणि समानानि भवन्ति यदा वृषभादिषु पञ्चसु च राशिषु चरति तदाहान्येव वर्धन्ते ह्रसति च मासि मास्येकैका घटिका रात्रिषु. ॥ ४ ॥
yada mesa-tulayor vartate tadaho-ratrani samanani bhavanti yada
vrsabhadisu pancasu ca rasisu carati tadahany eva vardhante hrasati ca
masi masy ekaika ghatika ratrisu.
yada-when; mesa-tulayoh-in Mesa (Aries) and Tula (Libra); vartate-the sun exists; tada-at that time; ahah-ratrani-the days and nights; samanani-equal in duration; bhavanti-are; yada-when; vrsabha-adisu-headed by Vrsabha (Taurus) and Mithuna (Gemini); pancasu-in the five; ca-also; rasisu-signs; carati-moves; tada-at that time; ahani-the days; eva-certainly; vardhante-increase; hrasati-is diminished; ca-and; masi masi-in every month; eka-eka-one; ghatika-half hour; ratrisu-in the nights.
When the sun passes through Mesa [Aries] and Tula [Libra], the durations of day and night are equal. When it passes through the five signs headed by Vrsabha [Taurus], the duration of the days increases [until Cancer], and then it gradually decreases by half an hour each month, until day and night again become equal [in Libra].