@register.filter
def astrological_sign(bday):
    if bday.month == 1 and bday.day >= 20 or bday.month == 2 and bday.day < 18:
        return 'aquarius'
    if bday.month == 2 and bday.day >= 18 or bday.month == 3 and bday.day < 20:
        return 'pisces'
    if bday.month == 3 and bday.day >= 20 or bday.month == 4 and bday.day < 20:
        return 'aries'
    if bday.month == 4 and bday.day >= 20 or bday.month == 5 and bday.day < 21:
        return 'taurus'
    if bday.month == 5 and bday.day >= 21 or bday.month == 6 and bday.day < 21:
        return 'gemini'
    if bday.month == 6 and bday.day >= 21 or bday.month == 7 and bday.day < 22:
        return 'cancer'
    if bday.month == 7 and bday.day >= 22 or bday.month == 8 and bday.day < 23:
        return 'leo'
    if bday.month == 8 and bday.day >= 23 or bday.month == 9 and bday.day < 23:
        return 'virgo'
    if bday.month == 9 and bday.day >= 23 or bday.month == 10 and bday.day < 23:
        return 'libra'
    if bday.month == 10 and bday.day >= 23 or bday.month == 11 and bday.day < 22:
        return 'scorpio'
    if bday.month == 11 and bday.day >= 22 or bday.month == 12 and bday.day < 22:
        return 'sagittarius'
    return 'capricorn'