import pandas as pd

d = pd.read_table('BatteryParkTideData_Cleaned.txt', sep='\s+', parse_dates=[[1, 2]])

d.head()

d['TimeOffset'] = d['Date_Time'] - d['Date_Time'][0]

d.head()

d['TimeOffsetHours'] = pd.Series(to.total_seconds() / 3600. for to in d['TimeOffset'])

d.to_csv('BatteryParkTideData.csv', na_rep='NA', cols=['TimeOffsetHours', 'Pred6', 'Backup', 'Acoustc'], index=False)