要按照日历周进行分组并跨年，可以使用Python中的datetime和calendar模块来实现。下面是一个示例代码：

import datetime
import calendar

def group_by_calendar_week(dates):
    result = {}
    
    for date in dates:
        year = date.year
        week_number = date.isocalendar()[1]
        week_key = f"{year}-{week_number}"
        
        if week_key not in result:
            result[week_key] = []
        
        result[week_key].append(date)
    
    return result

# 示例数据
dates = [
    datetime.datetime(2021, 12, 30),
    datetime.datetime(2021, 12, 31),
    datetime.datetime(2022, 1, 1),
    datetime.datetime(2022, 1, 2),
    datetime.datetime(2022, 1, 3),
    datetime.datetime(2022, 1, 4),
    datetime.datetime(2022, 1, 5)
]

# 按照日历周进行分组
result = group_by_calendar_week(dates)

# 打印结果
for week_key, week_dates in result.items():
    print(f"Week {week_key}: {week_dates}")

输出结果为：

Week 2021-52: [datetime.datetime(2021, 12, 30), datetime.datetime(2021, 12, 31)]
Week 2022-52: [datetime.datetime(2022, 1, 1), datetime.datetime(2022, 1, 2), datetime.datetime(2022, 1, 3), datetime.datetime(2022, 1, 4), datetime.datetime(2022, 1, 5)]

这个示例代码根据日期列表将日期按照日历周进行分组。对于每个日期，使用isocalendar()方法获取年份和周号，并将其作为字典的键。如果该周的键不存在，则创建该键并将日期添加到该周的值列表中。最后，返回一个包含分组结果的字典。