What is the duration of the four yugas as mentioned in the Vayu Purana?

Yathā vedaś catuṣpādaś catuṣpādaṁ tathā yugam।
Yathā yugaṁ catuṣpādaṁ vidhātrā vihitaṁ svayam॥
Catuṣpādaṁ purāṇaṁ tu brahmaṇā vihitaṁ purā॥

- vaayu puran (chapter 32.67)

Just as God has made the Vedas Chatushpad, similarly Brahmaji has also divided each Yuga into four padas.

The names of these four pada (quarters) are as follows-

1- Prakriya Pada
2- Anushang Pada
3- Upodghat Pada
4- Sanhar Pada

Satyayuga enjoys one pada, Tretayuga enjoys two padas, Dwaparyuga enjoys three padas and Kaliyuga enjoys four padas.

In these verses, the age of the four Yugas has been stated as 12,000 human years. The word 'Divya' has not been used in any verse, instead human years have been used. Hence it is clear that mysterious changes have been made in the Sanatan scriptures with time.

Vayu Purana (Chapter 32), Manusmriti

Catvāryāhuḥ sahastrāṇi varṣāṇāṁ ca kṛtaṁ yugam।
Tasya tāvac chatī sandhyā sandhyāṁśaś ca tathā vidhaḥ॥ 58

Kṛte vai prakriyāpādaśvatuhuśāhasra ucyate।
Tasmāc catuḥśataṁ sandhyā sandhyāṁśaś ca tathāvidhaḥ॥ 59

Kaliyug is 4,000 human years. Its 'Sandhya' is of 400 years and 'Sandhyamsha' is of 400 years. Thus Kaliyug is of 4,800 years and its one pada i.e. fourth part is 1,000. Satyayug has an age of 1,200 years.

Trētā trīṇi sahastrāṇi, saṅkhyayā munibhiḥ saha।
Tasyāpi triśatī sandhyā sandhyāṁ śastriśataḥ smṛtaḥ॥ 60
Anuṣaṅgapādastreṭāyāstrisāhasrastu saṅkhyayā।

Tretayug is of 3,000 human years and the duration of Tretayug is 3,600 human years including 300 years of Sandhya and 300 years of Sandhyamsha. This Tretayug experiences two parts, one is Procession Pada and the other is Anushang Pada. The years of both those Pada and accordingly the duration of Sandhya and Sandhyamsha together make Tretayug experience 3600 years.

Dvāpare he sahasre tu varṣāṇāṁ samprakīrtitam॥ 61
Tasyāpi dviśatī sandhyā sandhyāṁśo dviśatastathā।
Upodaghātastreṭīyastu dvāpare pāda ucyate॥ 62

this Dwaparyug experiences the duration of three padas. One is Processing pada, the second is Anushang pada and the third is Upodghat pada - the years of these three padas and accordingly 300-300 years of Sandhya and Sandhyaamsha together make the age of Dwaparyug 3,600 years.

Kali varṣa sahasrantu prāhuḥ
Saṅkhyāvido janāḥ।
Tasyāpi śatikā sandhyā
Sandhyāṁśaḥ śatameva ca॥ 63

Saṁhāra pādaḥ saṅkhyāś caturtho
Vai: kalau yuge।
Sasaṁdhyāni sahāṁśāni catvāri tu yugāni vai॥ 64

Kaliyug is of thousand years and its Sandhi is of 100 years and Sandhyaamsha is of 100 years, thus there are 1200 years, but Kaliyug enjoys the time of four padas, that is, one process pada, second Anushang pada, third Upodghata pada and fourth Sanhaar pada, thus 4,000 of four padas and accordingly 400 years of Sandhya and Sandhyaamsha, 400 years each, together Kaliyug enjoys the age of 4,800 years.

Etad dvādaśasāhasra caturyugam iti smṛtam।
Evaṁ pādaiḥ sahasrāṇi ślokānāṁ pañca pañca ca॥ 65

Sandhyāsadhyāṁśakaireva dve sahasra tathā'pare।
Evaṁ dvādaśasāhasra purāṇaṁ kavayo viduḥ॥ 66

The duration of all four yugas along with Sandhya and Sandhyamsha is said to be 12000 years. The sum of all these Yuga padas is 10000 years and Sandhya and Sandhyamsha are 2000 years. Thus the total duration of Yuga padas is said to be 12000 years.