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).