In an earthquake-prone country, construction date is one of the most important numbers on any Japanese listing. Two thresholds matter most.

The key dates

• 1981 (新耐震基準): the modern seismic standard. Buildings permitted after June 1981 are far more resilient.
• 2000: a further tightening for wooden houses, improving foundations and connections.

Pre-1981 buildings can still be sound but may need retrofitting, affect financing, and carry higher insurance. Always confirm the building-confirmation date — not just the listing’s “built” year — and factor seismic standard into both price and resale planning.