Ancient Indian measurement of time for a day.

The Sanathanic / Hindu system of measurement of time for a day
starts with a wink of the eye.
The wink makes us, the humans, differ from devas who do not wink.

(That is why they are known as ‘Imaiyavar’ in Tamil — those who don’t wink)
That means there is no time for them.

Time is applicable for us in the created world.

18 winks = 1 kashtam
30 kashtam = 1 kala
30 kala = 1 vinadi
60 vinadi = 1 naazhigai / ghati = 24 minutes

2 naazhigai / ghati = 1 muhurtha
30 muhurtha = 1 day = 24 hours

or

60 naazhigai / ghati = 1 day.

Another way is to take ‘truti’ as the basic unit.
Truti is the time taken for a needle to prick a lotus leaf.

60 truti = 1 prana (1 inhale + 1 exhale = 1 prana)
6 pranas = 1 vinadi
60 vinadi = 1 naazhigai
(and the rest continues as before.)

Another way of calculation is like this.

1 day = 10 jaamam.

10 jaamam = 30 muhurthas = 60 ghatis.

1 jaamam = 3 muhurthas = 6 ghatis

1 jaamam = 6 x 24 = 144 minutes = 2 hours, 24 minutes.

The further division of time until the basic unit is like this.

1 ghati / naazhigai = 60 vinadi / vighati = 24 minutes
1 vinadi = 60 lipta
1 lipta = 60 viliptas
1 vilipta = 60 para
1 para = 60 tatapras.

So a day was divisible into

60 x 60 x 60 x 60 x 60 x 60 =3,60,00,000 basal units of tatapara

according to Hindu system!!

Jaamam starts at sun rise at a place. Jaamams are calculated for Day and night. (sun rise to sun set and from sunset to sunrise) There are 5 jaamams in day and 5 in night. Depending on sun rise and sun set timings, the duration of jammam will change for different places.

Divide the day / night into 5 equal parts. Each will be a jaamam. It is basically calculated in nazhigai basis only. If we assume that the day / night has 30 naazhigai, each jaamam will have 6 naazhigai = 6 x 24 minutes = 2 hrs and 24 minutes.

Nowadays we just divide the time of day / night duration into 5 and count the hrs & minutes from sun rise at a place.