Vedic Clock

This is an illustration of what a Vedic clock might look like, based on A. C. Bhaktivedanta Swami's translation of the eleventh chapter of the third canto of the Śrīmad-Bhāgavatam. It features all time scales, from the shortest to the longest, just like our Western clock has arms for hours, minutes and seconds. It also demonstrates how the Vedic understanding of time is cyclic rather than linear. Even the longest cycle, the lifetime of Brahmā, is repeated endlessly, without beginning or end.

1 truṭi ≈ 0.59 milliseconds
1 vedha = 100 truṭi ≈ 59 milliseconds
1 lava = 3 vedha ≈ 0.18 seconds
1 nimeṣa = 3 lava ≈ 0.53 seconds
1 kṣaṇa = 3 nimeṣa = 1.6 seconds
1 kāṣṭhā = 5 kṣaṇa = 8 seconds
1 laghu = 15 kāṣṭhā = 2 minutes
1 daṇḍa = 15 laghu = 30 minutes
1 muhūrta = 2 daṇḍa = 1 hour
1 yāma = 3 muhūrta, or 6 daṇḍa = 3 hours
1 ahanī (day) = 8 yāma = 24 hours
1 pakṣa (fortnight) = 15 ahanī = 15 days (day or night on pitā planets)
1 māsa (month) = 2 pakṣa = 30 days (day and night on pitā planets)
1 ritu (season) = 2 māsa = 60 days
1 ayana (sun movement) = 3 ritu = 180 days
1 saṁvatsara (year) = 2 ayana = 360 days (day and night on heavenly planets)
1 year of the demigods = 360 saṁvatsara = 360 years
1 mahā-yuga = 12,000 years of the demigods = 4,320,000 years
1 manvantara (lifespan of Manu) = 71 mahā-yuga = 306,720,000 years
1 kalpa (day or night of Brahmā) = 1000 mahā-yuga, or 14 manvantara plus 15 sandhyā = 4,320,000,000 years
1 day and night of Brahmā = 2 kalpa = 8,640,000,000 years
1 month of Brahmā = 30 days and nights of Brahmā = 259,200,000,000 years
1 year of Brahmā = 12 months of Brahmā = 3,110,400,000,000 years
1 parārdha = 50 years of Brahmā = 156,764,160,000,000 years
1 mahā-kalpa (lifespan of Brahmā) = 2 parārdha, or 100 years of Brahmā = 313,528,320,000,000 years

The duration of the two parts of Brahmā’s life, as above mentioned, is calculated to be equal to one nimeṣa (less than a second) for the Supreme Personality of Godhead, who is unchanging and unlimited and is the cause of all causes of the universe.
— Śrīmad-Bhāgavatam, canto 3, chapter 11, verse 38

The reasons that this is merely an approximation, and a "Vedic wristwatch" would be difficult to produce, are mainly:

There are Vedic calendars, but they are calculated separately for each location, depending on astronomical observations or calculations of the time of sunrise at that location, and the phase of the moon at that time.

Sources of information: