New York — the reference clock for US business
New York runs on Eastern Time (EST/EDT). It's the reference timezone for US business — Wall Street opens 9:30 AM ET (NYSE, NASDAQ), most US Fortune 500 anchor their internal clocks to ET regardless of headquarters. Multi-office US meeting invites default to "ET" in the timezone field. The city aligns with Toronto (same offset), sits 5 h behind London (winter) / 4 h behind (summer).