Day 189, 12:00, for 12 hours: 132 zombies at ×39 health and ×42 attack.
Part of Endless tier 38, day 4 of 5.
When it ends: 
All-Purpose Strengthener
Fine Sheet Metal
Tempered Glass
Scrap Metal
Cold Cuts
Mystery Novel (Endless rewards, tiers 30-40)
Day 189, 12:00, for 12 hours: 132 zombies at ×39 health and ×42 attack.
Part of Endless tier 38, day 4 of 5.
When it ends: All-Purpose StrengthenerFine Sheet MetalTempered GlassScrap MetalCold CutsMystery Novel (Endless rewards, tiers 30-40)