Time is compared here (SB 3.21.18) to a big wheel which has 360 joints, six rims in the shape of seasons, and numberless leaves in the shape of moments. It rotates on the eternal existence, Brahman
SB Canto 3
Your wheel, which has three naves, rotates around the axis of the imperishable Brahman. It has thirteen spokes, 360 joints, six rims and numberless leaves carved upon it. Though its revolution cuts short the life-span of the entire creation, this wheel of tremendous velocity cannot touch the life-span of the devotees of the Lord.
The time factor cannot affect the span of life of the devotees. In Bhagavad-gītā it is stated that a little execution of devotional service saves one from the greatest danger. The greatest danger is transmigration of the soul from one body to another, and only devotional service to the Lord can stop this process. It is stated in the Vedic literatures, hariṁ vinā na mṛtim taranti: without the mercy of the Lord, one cannot stop the cycle of birth and death. In Bhagavad-gītā it is stated that only by understanding the transcendental nature of the Lord and His activities, His appearance and disappearance, can one stop the cycle of death and go back to Him. The time factor is divided into many fractions of moments, hours, months, years, periods, seasons, etc. All the divisions in this verse are determined according to the astronomical calculations of Vedic literature. There are six seasons, called ṛtus, and there is the period of four months called cāturmāsya. Three periods of four months complete one year. According to Vedic astronomical calculations, there are thirteen months. The thirteenth month is called adhi-māsa or mala-māsa and is added every third year. The time factor, however, cannot touch the lifespan of the devotees. In another verse it is stated that when the sun rises and sets it takes away the life of all living entities, but it cannot take away the life of those who are engaged in devotional service. Time is compared here to a big wheel which has 360 joints, six rims in the shape of seasons, and numberless leaves in the shape of moments. It rotates on the eternal existence, Brahman.