No. Of Working Days In A Month

Hello Professionals,
I am Krishna working as a HR in a IT company based out of vizag. I need your inputs in a query which relates to payroll.
How many days an IT company has to consider in any particular month while processing payroll??
1. Is it actual working days like 21,22 etc...???
2. Is it a standard calendar days 30???
3. Is it 30 days in Apr, Jun, Sep, Nov and 31 days in Jan, Mar, May, Jul, Aug, Oct and Dec and 28/29 days in Feb???
Please share your thoughts.
Thanks in advance!!!

Please take a look at the below blog post in this regard -
Base days for monthly salary calculation

Hello Tegautham....
Thanks a lot for the quick response. I have gone through that link and i can conclude, there is no specified law about the no. of working days to be counted except in Gratuity Act.
Once again Thanks!!!