formatDate was parsing UTC timestamps in local time, shifting dates
back a day in western timezones. Strip the time portion before parsing
so dates display correctly.
Revert interest calculation from daily accrual back to standard monthly
compounding (rate/12) with per-payment rounding. This matches how
mortgage servicers calculate interest and produces correct amortization
schedules.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>