Find Best Meeting Time Across Time Zones in Python

from datetime import datetime, timedelta, timezone
from zoneinfo import ZoneInfo
from dataclasses import dataclass
from typing import List, Tuple, Optional

@dataclass
class Participant:
    name: str
    timezone: str
    # weekdays availability: 0=Mon, start_hour (0-23), end_hour (0-23)
    available_slots: List[Tuple[int, int, int]]  # (weekday, start_hour, end_hour)

def find_best_meeting_time(participants: List[Participant], duration_hours: int = 1) -> Optional[str]:
    best_overlap = []
    for weekday in range(5):  # Monday-Friday
        # Convert participants' slots to UTC
        utc_slots = []
        for p in participants:
            tz = ZoneInfo(p.timezone)
            for (wday, start_h, end_h) in p.available_slots:
                if wday != weekday:
                    continue
                # Convert to UTC by finding that weekday in 2025-01-06 (a Monday)
                ref_date = datetime(2025, 1, 6 + weekday, tzinfo=tz)  # correct weekday
                # Actually, easier: use a reference date and compute local times
                base_local = datetime(2025, 1, 6 + weekday, tzinfo=tz)  # Monday 2025-01-06 is Monday
                utc_start = base_local.replace(hour=start_h).astimezone(timezone.utc)
                utc_end = base_local.replace(hour=end_h).astimezone(timezone.utc)
                utc_slots.append((utc_start.hour, utc_end.hour))
        # Find overlapping hours across all participants for this weekday
        for hour in range(24):
            all_available = True
            for (start_h, end_h) in utc_slots:
                if not (start_h <= hour <= end_h - duration_hours):
                    all_available = False
                    break
            if all_available:
                best_overlap.append((weekday, hour))
    if not best_overlap:
        return "No common time found"
    # Convert best slot back to each participant's local time
    weekday_names = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]
    wd, utc_hour = best_overlap[0]
    result_str = f"Suggested time (UTC): {weekday_names[wd]} at {utc_hour:02d}:00\n"
    for p in participants:
        tz = ZoneInfo(p.timezone)
        local_dt = datetime(2025, 1, 6 + wd, utc_hour, tzinfo=timezone.utc).astimezone(tz)
        result_str += f"  {p.name}: {local_dt.strftime('%A %H:%M %Z')}\n"
    return result_str

if __name__ == "__main__":
    participants = [
        Participant("Alice", "America/New_York", [(0, 9, 17), (1, 9, 17)]),
        Participant("Bob", "Europe/London", [(0, 14, 20), (1, 14, 20)]),
        Participant("Charlie", "Asia/Tokyo", [(0, 10, 18), (1, 10, 18)]),
    ]
    print(find_best_meeting_time(participants, duration_hours=1))