Finding an element of pandas series at a certain time (date)
If your dataframe is indexed by date, you can:

df[date] to access all the rows indexed by such date (e.g. df['2019-01-01']);
df[date1:date2] to access all the rows with date index between date1 and date2 (e.g. df['2019-01-01': '2019-11-25']); 
df[:date] to access all the rows with index before date value (e.g. df[:'2019-01-01']);
df[date:] to access all the rows with index after date value (e.g. df['2019-01-01':]).
I have some pandas series with the type "pandas.core.series.Series". I know that I can see its datetimeindex when I add ".index" to the end of it. 
But what if I want to get the element of the series at this time? and whats if I have a "pandas._libs.tslibs.timestamps.Timestamp" and want to get the element of the series at this time?