Denver, Colorado · MST/MDT (UTC-7) · United States
Denver, Boulder, Littleton — Denver metro core
Original 1947 code. Mile High City at 5,280 feet elevation.
Dial 1 + 303 + 7-digit number for calls from outside the area. Local calls within the same area code may use 7-digit dialing where available.
From outside United States: dial your country's exit code + 1 + 303 + number. From most countries, the format is +1-303-XXX-XXXX.
Area code 303 is in MST/MDT (UTC-7). Business hours are typically 9:00 AM – 5:00 PM local time. Remember that clocks shift during DST (March–November).
While (303) is a legitimate area code, scammers can spoof any number. Never share personal info with unknown callers. Verify by calling the organization directly.
Area code data sourced from NANPA. Timezone data from IANA Time Zone Database. Last updated March 2026.