Why Vedang Jyotisha says 1 Yuga duration Is 5 Years which is different from Puranas

Question

Puranas says One Yuga Is Thousands of year old but Vedang Jyotisha says it's only of 5 years. Is Vedang Jyotisha and Puranas are talking about different Yugas?

Answer 1

Vedāṅgajyotiṣa is talking about a diff. yuga than commonly known one, OP has in mind.

The term yuga is commonly used for three different durations in śāstras -
5 yrs, Kṛta/Tretā/Dvāpara/Kali, and mahāyuga (caturyuga + sandhyāṁśas)
The latter two are amply mentioned in Siddhāntas & Purāṇas.
The 5 yr yuga would be represented in an italicized manner (yuga) for simplicity.

Yuga is mentioned in not only Vedāṅgajyotiṣa, but also in śruti & Purāṇas. This yuga consists of 62 candramāsas (synodic months), 1830 days and 1860 tithis (1/30th part of a synodic month) and was taken to commence at the winter solistice. At the time of Vedāṅgajyotiṣa, winter solstice occurred at the beginning of the first tithi of śuklapakṣa of the Māgha māsa. There are two adhimāsas (intercalary months) in a yuga. The sun & moon are supposed to occupy the same position at the beginning of each subsequent yuga and all the happenings would be repeated in the subsequent yugas in the same way. (Achar, 1997).

The constituent years of a yuga are called - saṁvatsara, parivatsara, idāvatsara, anuvatsara, & vatsara. In Ṛgveda saṁhitā (7.103.7-8) , saṁvatsara and parivatsara are mentioned. Taittirīya saṁhitā (5.5.7.1-3), Vājasaneyi saṁhitā (27.45 and 30.16), Taittirīya Brāhmaṇa (3.4.11 and 3.10.4), & Śatapatha Brāhmaṇa (8.1.4.8) give the names of all the five years of yuga, although, there's some variation in the names. Taittirīya saṁhitā calls them saṁvatsara, parivatsara, idāvatsara, iduvatsara, and vatsara, while the Vājasaneyi saṁhitā, Śatapatha Brāhmaṇa, and Taittirīya Brāhmaṇa calls them saṁvatsara, parivatsara, idāvatsara, idvatsara, and vatsara respectively. Aṁhasaspati & Saṁsarpa are the two adhimāsas (intercalary months) in a yuga, which is mentioned in Taittirīya saṁhitā (1.4.14). Arthaśāstra (2.20.64-66) refers to a yuga with two adhimāsas, which are inserted at the middle of the 3rd yr & at the end of the 5th. Bhīṣma mentions this too in Virāṭaparva (4.51.3 - pañcame pañcame varṣe dvau māsāv upajāyataḥ).

Following are some other śāstras, which mention yuga (i.e. of 5 yrs) -

saṁvasarastu prathamo dvitīyaḥ parivatsaraḥ //
iḍvatsarastṛtīyaśca caturthānuvatsaraḥ /
pañcamo vatsarasteṣāṁ kālaḥ yusañjñitaḥ //
~ Brahmāṇḍa Purāṇa (1.13.114b-115)

saṁvatsaraḥ parivatsara iḍāvatsara eva ca /
anuvatsaro vatsaraśca viduraiva prabhāṣyate //
~ Bhāgavata Purāṇa (3.11.14)

saṁvatsarādayaḥ pañca caturmāsavikalpitāḥ /
niścayaḥ sarvakālasya yugamityabhidhīyate //
saṁvatsarastu prathamo dvitīya parivatsaraḥ /
idvatsarastṛtīyastu caturthaścānuvatsaraḥ /
vatsaraḥ pañcamaścātra kālo'yaṁ yugasañjñitaḥ //
~ Viṣṇu Purāṇa (2.8.71-72)

saṁvatsaro'gniḥ parivatsaro'rka idādikaḥ śītamayūkhamālī /
prajāpatiścāpyanuvatsaraḥ syādidvatsaraḥ śailasutāpatiśca //
~Bṛhatsaṁhitā (8.24)

So, it's not like yuga (i.e. of 5 yrs) is not a concept present in Purāṇas. Furthermore, as shown above, it has mentions in Kauṭilya's Arthaśāstra, Mahābhārata, Bṛhatsaṁhitā, etc.

Answer 2

The Yajur Veda one also uses a Yuga of 19 years if I remember correctly.

No one has cursed a Yuga to be of a certain length. It simply means a cycle or age.

There was the Yuga of your grandfather, now is the Yuga of your father, later, it will be your Yuga.

That is completely fine to say.

Even a Kalpa or Manvantara can be said to be a Yuga. A single year and a single lunar month are also Yugas.

Does that mean the 4.32 million years Mahayuga cycle isn't true? No, it's true as well as this is true.

Spend some time around basic dictionaries and you'll get to know this. Although, it's pretty much common sense. Well, at-least no one started claiming 4.32 million years Mahayuga as interpolation yet, lol.