The law does not choose to define business hours for a company as this could be best left to the convenience of each company.Each company has its own schedule of business hours and this is well known to the public with whom it deals vide McA's File No. 34/1/75-CL-III[Reference: Ramaiya's Guide to the Companies Act,1956 (17th Edition,Part-2,page-1954.
In view of the above, an AGM is required to be held during the usual business hours of the Company other than on Public Holiday(or Saturday where according to the standing instruction of the Company ,Saturday has been declared as a non-working day for usual business purposes)at the Registered Office of the Company or any other place within the city ,town or village in which the registered office of the Company is situated vide practical notes given in page 600 in the book titled "Guide to Co. Law Procedures by Shri M.C.Bhandari (Volume2).
Hope this will clarify your doubt now in the matter.
A.K.Maitra.M.Com,LL.B,A.C.A,A.C.S,M.I.M.A
Retd. Co.Secy. & G.M.(Law)
National Fertilizers Ltd.
(A Mini-Ratna Central P.S.U.)