以下是一个示例程序，可以根据输入的日期来判断所属的季节：

def get_season(date):
    # 将输入的日期转换为月份和日期
    month, day = date.split('-')
    month = int(month)
    day = int(day)

    # 根据月份和日期判断季节
    if (month == 1 and day >= 1) or (month == 2 and day <= 28) or (month == 3 and day <= 31):
        season = "冬季"
    elif (month == 4 and day >= 1) or (month == 5 and day <= 31) or (month == 6 and day <= 30):
        season = "春季"
    elif (month == 7 and day >= 1) or (month == 8 and day <= 31) or (month == 9 and day <= 30):
        season = "夏季"
    elif (month == 10 and day >= 1) or (month == 11 and day <= 30) or (month == 12 and day <= 31):
        season = "秋季"
    else:
        season = "无效日期"

    return season

# 输入日期，格式为YYYY-MM-DD
date = input("请输入日期（YYYY-MM-DD）：")
season = get_season(date)
print("该日期所属的季节是：", season)

使用示例：

请输入日期（YYYY-MM-DD）：2021-07-15
该日期所属的季节是： 夏季

请注意，此示例仅考虑了公历日期，尚未考虑闰年的情况。如果需要考虑闰年，请在代码中进行相应的调整。