from datetime import datetime

def normalize_date(date_str):
    if not date_str or str(date_str).lower() in ["null", "none", "unknown"]:
        return datetime.today().strftime("%Y-%m-%d")
    
    formats = ["%Y-%m-%d", "%d-%m-%Y", "%d/%m/%Y", "%m/%d/%Y", "%Y/%m/%d", "%d %b %Y", "%B %d, %Y"]
    clean = str(date_str).strip()
    
    for fmt in formats:
        try:
            return datetime.strptime(clean, fmt).strftime("%Y-%m-%d")
        except ValueError: continue
            
    return datetime.today().strftime("%Y-%m-%d")