title: getting could not convert string to Timestamp error when trying pass pandas series data to date_range fucntion
body: <p>I am trying to pass pandas series data to date_range fun and i am getting below error ,How can i cast string type to timestamp in pandas</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  from pandas.tseries.offsets import CustomBusinessHour
  from pandas.tseries.holiday import USFederalHolidayCalendar
  
  data = {
      'start': ['2019-08-23 00:01:46.697000',
                '2018-10-29 19:01:10.887000',
                '2018-10-22 17:42:24.467000'],
      'end': ['2019-08-26 17::00.830000',
              '2018-11-27 09:31:39.967000',
              '2018-11-28 18:33:35.243000' ]
  }
  df = pd.DataFrame(data)
  
  bh = CustomBusinessHour(calendar=USFederalHolidayCalendar(), start='00:01', end='23:59')
  
  def f(x):
      idx = pd.date_range(start=x.start, end=x.end, freq= bh)
      mask = ~((idx.dayofweek == 0) &amp; (idx.hour &lt;= 7))
      return len(idx[mask])
  
  df['Hours_diff'] = df.apply(f, axis=1)
  print(df.head(10))
  </code></pre>
  
  <p>File "pandas/_libs/tslibs/timestamps.pyx", line 748, in pandas._libs.tslibs.timestamps.Timestamp.<strong>new</strong>
    File "pandas/_libs/tslibs/conversion.pyx", line 288, in pandas._libs.tslibs.conversion.convert_to_tsobject
    File "pandas/_libs/tslibs/conversion.pyx", line 487, in pandas._libs.tslibs.conversion.convert_str_to_tsobject
  ValueError: ('could not convert string to Timestamp', u'occurred at index 0')</p>