TypeError: Only valid with DatetimeIndex, TimedeltaIndex or PeriodIndex, but got an instance of Int64Index

df['date'] = pd.to_datetime(df['date'])
df = df.set_index('date') 
weekly_summary = df.story_point.resample('W').sum()

df['date'] = pd.to_datetime(df['date'])
df = df.set_index('date') 
weekly_summary = df.story_point.resample('W').sum()

df['date'] = pd.to_datetime(df['date'])
df = df.set_index('date') 
weekly_summary = df.story_point.resample('W').sum()

df['date'] = pd.to_datetime(df['date'])
df = df.set_index('date') 
weekly_summary = df.story_point.resample('W').sum()

df['date'] = pd.to_datetime(df['date'])
df = df.set_index('date') 
weekly_summary = df.story_point.resample('W').sum()

df['date'] = pd.to_datetime(df['date'])
df = df.set_index('date') 
weekly_summary = df.story_point.resample('W').sum()

df['date'] = pd.to_datetime(df['date'])
df = df.set_index('date') 
weekly_summary = df.story_point.resample('W').sum()

df['date'] = pd.to_datetime(df['date'])
df = df.set_index('date') 
weekly_summary = df.story_point.resample('W').sum()

df['date'] = pd.to_datetime(df['date'])
df = df.set_index('date') 
weekly_summary = df.story_point.resample('W').sum()

df['date'] = pd.to_datetime(df['date'])
df = df.set_index('date') 
weekly_summary = df.story_point.resample('W').sum()