Calculation of time limit in companies act 2013

While calculation any time limit in companies act 2013 first day is excluded or not.
e.g. If it is given that "The ditector may, within 30 days of resignation, forward to the registrar..." then if the director resigned on 1st September then the intimation will be given on or before 30th september or it will be given on or before 1st October.
Also whether the method of calculating time period will deffer from provision to provision based on usage of words "from" or "of".