How to calculate volunteer time

We have a number of various volunteers on our Townscape Heritage project supporting a wide range of activities from attending community events to assisting our consultants in the development of a Characterisation study. Whilst some of these activities fall naturally under a HLF volunteer category i.e. Skilled/ Unskilled labour others are more unclear. If anyone has any further guidance on this, it would be greatly appreciated.

Also, when recording volunteer time the claim form requests number of volunteer days, however much work tends to be based on hours. I'd be interested to know how projects calculate their volunteer 'days'.

How many hours do you use to make a day?

Do you use your own organisations working day as a basis?