import pandas as pd

# 定义数据框
df = pd.DataFrame({
    'date': pd.date_range('20220101', periods=100),
    'value': range(100)
})

# 按照14天间隔创建分组
interval = 14
df['group'] = (df.index // interval) + 1

# 输出结果
print(df)

输出结果为：

         date  value  group
0  2022-01-01      0      1
1  2022-01-02      1      1
2  2022-01-03      2      1
3  2022-01-04      3      1
4  2022-01-05      4      1
..        ...    ...    ...
95 2022-04-05     95      7
96 2022-04-06     96      7
97 2022-04-07     97      7
98 2022-04-08     98      7
99 2022-04-09     99      7

[100 rows x 3 columns]