For Naraki and Dev jeev, the “body formation time” (janma-samay) is extremely short compared to humans.

In Jain texts, both:

• Deva (heavenly beings) and
• Nārakī (hell beings)

are described as upapāduka beings – they are spontaneously born. That means:

• There is no long garbh-kāl (womb period) like in humans or animals.
• The body is formed instantly at the very moment of birth, along with its full size appropriate to that gati and level.
• So, the “time taken to complete the body” is considered one samaya only (the smallest indivisible unit of time), practically “immediate”.

Differences:

• Human / tiryanch (animal) gati → usually have garbhaj birth, with a period in the womb and gradual body formation.
• Dev & Naraki gati → upapāduka birth, no gradual formation, body appears complete at once.

So, both Narki and Dev jeev complete their body instantly at birth; there is no extended time like hours, days or months.