The earliest Modern tournament I have access to is from March 2, 2024. The database contains two tournaments from that date: "Axion Now MEGA Modern" starting at 10:00 AM and "The Gathering Showdown Series" starting at 4:00 PM.
The tournament data spans from March 2024 through the current date (September 2025), providing about 18 months of comprehensive Modern format coverage. All early tournaments appear to be sourced from Melee tournament management system.
Sources: Data coverage begins March 2, 2024. Sample tournaments include Axion Now MEGA Modern and regional championship qualifiers from early March 2024.