Constant zebra_chain::parameters::network::subsidy::PRE_BLOSSOM_HALVING_INTERVAL

pub const PRE_BLOSSOM_HALVING_INTERVAL: HeightDiff = 840_000;

Halving is at about every 4 years, before Blossom block time is 150 seconds.

(60 * 60 * 24 * 365 * 4) / 150 = 840960