Time Ago 포매터

from datetime import datetime, timezone

def time_ago(past: datetime, now: datetime = None) -> str:
    """Return human-readable relative time string."""
    if now is None:
        now = datetime.now(timezone.utc)
    diff = now - past
    total_seconds = int(diff.total_seconds())
    if total_seconds < 0:
        return "in the future"

    minutes = total_seconds // 60
    hours = minutes // 60
    days = hours // 24
    months = days // 30
    years = days // 365

    if total_seconds < 60:
        return f"{total_seconds} second{'s' if total_seconds != 1 else ''} ago"
    elif minutes < 60:
        return f"{minutes} minute{'s' if minutes != 1 else ''} ago"
    elif hours < 24:
        return f"{hours} hour{'s' if hours != 1 else ''} ago"
    elif days < 30:
        return f"{days} day{'s' if days != 1 else ''} ago"
    elif months < 12:
        return f"{months} month{'s' if months != 1 else ''} ago"
    else:
        return f"{years} year{'s' if years != 1 else ''} ago"

# Examples
from datetime import timedelta
now = datetime(2025, 6, 15, 12, 0, 0, tzinfo=timezone.utc)
print(time_ago(now - timedelta(seconds=30), now))   # 30 seconds ago
print(time_ago(now - timedelta(minutes=45), now))   # 45 minutes ago
print(time_ago(now - timedelta(days=3), now))       # 3 days ago
print(time_ago(now - timedelta(days=400), now))     # 1 year ago