The altcoin season has no fixed date, primarily looking at two signals: the altcoin season index ≥ 75 (over 75% of the top 50/100 large-cap altcoins outperform Bitcoin over the past 90 days) and a decline in Bitcoin's dominance. Combining history with the 2025 market:

1. Historical patterns: It often starts 1-2 years after Bitcoin's halving, in the midst of a bull market; in 2017, it exploded about a year after BTC's halving, and in 2021, it started within six months after the halving.

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2. Current situation in 2025 (as of December 17): The altcoin season index has risen to 71, approaching the 75 threshold; BTC's dominance has dropped below 57%, funds are beginning to rotate, and analysts generally believe that December is a critical window period, making a full altcoin season likely to officially start this month until early 2026.