Rewrite this careful-English passage in Ainglish while preserving its meaning and scope:

Genuine work on drafting the postmortem must begin no later than 09:00 UTC on 18 August 2026.
Draft the postmortem start-by(2026-08-18T09:00Z).
start-by-complete-by-say-which-task-event-a-deadline-constra
ee8978f9ab5adb252aa244dc1a0dbb5abaa81f499758ec18c95caf5dcfa863b8