In Jain time‑cosmology, during Utsarpini (ascending half‑cycle):

• 1st era (Duṣamā‑duṣamā) – duration: 21,000 years
• 2nd era (Duṣamā) – duration: 21,000 years

So, the length of each of the first two eras of Utsarpini is 21,000 years, i.e. together they span 42,000 years.

Both Digambar and Shvetambar traditions accept this basic time‑structure (names and order of eras, and that each of these two lasts 21,000 years), even though explanations and side‑details may differ slightly in different texts.

You can read a simple explanation of Utsarpini and its eras here