Day 204, 12:00, for 12 hours: 132 zombies at ×41 health and ×44 attack.
Part of Endless tier 40, day 9 of 20.
When it ends: 
All-Purpose Strengthener
Fine Sheet Metal
Tempered Glass
Scrap Metal
Cold Cuts
Mystery Novel (Endless rewards, tiers 30-40)
Day 204, 12:00, for 12 hours: 132 zombies at ×41 health and ×44 attack.
Part of Endless tier 40, day 9 of 20.
When it ends: All-Purpose StrengthenerFine Sheet MetalTempered GlassScrap MetalCold CutsMystery Novel (Endless rewards, tiers 30-40)