Python- How to format datetime and replace value by multiple datetime conditions

1 Format datetime 

sample un-formatted date in my dataset:

17-Jan-18 use "%d-%b-%y" to impute , which changes to 2017-01-18

Aug 20,2017 , use %b %d, %Y" to impute 

other version see reference: http://strftime.org/

所有的format都是有跡可循，先按照原本的format去讀，再change to format datetime. 這樣就可以使用<,>，=來subset particular date interval. i.e. Aug, 這樣月的縮寫，用%b去讀，August用%B去讀。use lambda apply to whole column. 

def format_date1(x, col_name):
    s = x[col_name]    
    return datetime.strptime(s,'%d-%b-%y')
data['Day'] =  data.apply(lambda x: format_date1(x, 'Day'), axis=1)

def format_date2(x, col_name):
    s = x[col_name]    
    return datetime.strptime(s,'%b %d, %Y')
data['Day'] =  data.apply(lambda x: format_date2(x, 'Day'), axis=1)

data.sort_values(by="Day")

2. data processing with datetime conditions 

i.e. 

data.loc[(data['Day']>='2017-07-10') & (data['Day']<="2017-07-30"),'Headline 2'] = "3 For Free Sale"

data.loc[data.Campaign == "First - Bath Tampa Bay", 'Headline 1'] = "One Day Bath Remodels"