import pandas as pd
df=pd.read_csv('yourfile.csv')

df.columns=pd.to_timedelta(pd.Series(range(df.shape[1]))*7,'d')+pd.to_datetime('2019-04-19')

from datetime import datetime, timedelta

columns = ['New_%s' % str(i).zfill(2) for i in range(1,107)]
fmt = '%B %d, %Y'
start_date = 'April 19, 2019'
current = datetime.strptime(start_date, fmt)
date_columns = [datetime.strftime(current - timedelta(days = 7 * i), fmt) for i, _ in enumerate(columns)]

['April 19, 2019',
 'April 12, 2019',
 'April 05, 2019',
 'March 29, 2019',
 'March 22, 2019',
 'March 15, 2019',
 'March 08, 2019',
 'March 01, 2019',
 'February 22, 2019',
 'February 15, 2019',
 'February 08, 2019',
 ...
]