Which Comes First, Night Or Day?

Nachiketas spent three days in Yamaloka without food.
It was a dangerous situation.
Yamadutas cautioned Yamaraja: taking care of a guest is not even by choice.
If the unexpected guest goes back unattended, it spells disaster for the host.
Yamaraja is aware of this.
Yamaraja wants to compensate for this dereliction.
He tells young boy Nachiketas.
तिस्रो रात्रीर्यदवात्सीर्गृहे मे- ऽनश्नन् ब्रह्मन्नतिथिर्नमस्यः। नमस्तेऽस्तु ब्रह्मन् स्वस्ति मेऽस्तु तस्मात्प्रति त्रीन्वरान्वृणीष्व॥
You stayed for three nights here at my home.
Without food.
I want to make up for that. please ask for three boons from me.
Otherwise, I will be doomed.
Why?
We have seen this in the earlier episode.
The guest is fire.
Any guest is like fire.
He needs to be taken care of, pacified.
An unattended guest even if he is the calmest person in the world, most peaceful person in the world, he can burn down the house of the host.
Just for the mere reason that the host is not doing his duty.
You can not afford to be careless with fire.
Yamaraja is scared now.
He is trying to pacify Nachiketas.
Namasyaha - you deserve honor and respect.
Two times he addresses Nachiketas as brahman:
ब्रह्मन्नतिथिर्नमस्यः । नमस्तेऽस्तु ब्रह्मन् ॥
Yamaraja is eager that Nachiketas should not feel offended.
It is like saying: I am so sorry. I am so sorry, saying it again and again.
Here there is an interesting point.
Why is it that Yamaraja says that you have spent three nights at my place instead of saying three days?
There are two reasons.
In the Vedic system, night comes first, then day.
For the person who does Agni upasana, first is the evening homa then the morning homa.
If you are unable to do it for some time due to say impurity in the family and then have to restart; you should not start with the morning homa, you should start with the evening homa.
The first part is the evening homa the second part is the morning homa.
First night then day.
Importance is given to night.
In the same way, first comes Krishna paksha then comes Shukla paksha.
This is the Vedic system.
Another point is.
Uttarayana is daytime for Devas.
Dakshinayana is nighttime for Devas.
Dakshina means South.
South is the direction of Yama.
He resides in the south.
That's another reason night is important for Yama.
This concept is there throughout Vedic literature.
When Shringi curses Raja Parikshit, he says before the seventh night from now he will be killed by Takshaka.
Default is night, counting nights.