How long is a "month" in a contract?

[Energize]

In my employment contract it states that I have one months notice, but in my redundancy letter for payment in lieu it says 4 weeks notice. Is a "month" not just taken to mean one months normal salary or 22 working days? A "month" is not defined in my employment contract.

 

[Energize]

I'm paid in 12 installments a year, I'm being paid in lieu of my 1 month notice period. £200 is worth taking it to court for me considering court fees are only £25. I will contact the above to clarify.

EDIT - I've got it sorted, it's a full months salary.