Try this one out, analyze result step by step.
declare @string varchar(max)
declare @subString varchar(max)
set @string = 'this is a duplicated question, but may get some new answers, since tech chagne from time to time as we know';
set @subString = 'this is a duplicated question, but may get some new answers, since tech chagne from time to time'
--Find the string.lastIndexof(time)
select LEN(@String)
select LEN(@SubString)
select CHARINDEX('time', REVERSE(@string))
select reverse(@string)
select reverse('time')
SELECT LEN(@string) - CHARINDEX(reverse('time'), REVERSE(@string)) - Len('time') + 1